MOSTPLUS 674-522 Left + 674-732 Right Exhaust Manifold Catalytic Converter Set – Complete Replacement Solution for Chevy and GMC Trucks

When your check engine light illuminates and diagnostic codes point to catalytic converter failure, you’re faced with a critical decision: pay thousands at the dealership or find a reliable aftermarket solution. After extensive hands-on evaluation of the MOSTPLUS 674-522 and 674-732 exhaust manifold catalytic converter set, we’re confident in recommending this complete replacement kit as a cost-effective alternative that doesn’t compromise on quality or performance.

This comprehensive two-piece system replaces both the left and right exhaust manifold catalytic converters on compatible Chevy Silverado, Tahoe, GMC Sierra 1500, and Yukon XL models. During our testing period, we discovered that MOSTPLUS has engineered a solution that addresses the common failure points of OEM converters while maintaining strict emissions compliance—all at a fraction of dealer pricing.

Why Your Vehicle Needs This Exhaust Manifold Catalytic Converter Replacement

Manifold-mounted catalytic converters operate in extreme conditions, positioned directly against your engine where temperatures regularly exceed 1,400°F. Over time—typically between 80,000 and 150,000 miles—these converters degrade internally, leading to reduced efficiency, failed emissions tests, and those dreaded P0420/P0430 diagnostic codes.

We’ve seen firsthand how deteriorated converters impact vehicle performance: reduced power output, decreased fuel economy (sometimes by 15-20%), rough idling, and that sulfuric “rotten egg” smell. The MOSTPLUS replacement set addresses these issues with fresh catalytic substrates that restore proper exhaust flow and emissions control to factory specifications.

Direct-Fit Engineering: What Sets This Converter Set Apart

One of our primary concerns when evaluating aftermarket exhaust components is fitment accuracy. Nothing derails a DIY installation faster than discovering bolt holes don’t align or flanges require modification. The MOSTPLUS manifold converter set impressed us with its precise engineering.

Exact OEM Specifications

These converters are manufactured to match the exact dimensions, mounting points, and flange configurations of the original equipment. During our installation testing on a 2008 Silverado 1500, every mounting point aligned perfectly without requiring elongated bolt holes, gasket adjustments, or creative problem-solving. The bolt patterns match OEM specifications precisely, and the oxygen sensor ports are positioned exactly where they need to be.

Quality Catalytic Substrate Technology

The heart of any catalytic converter is its substrate—the honeycomb structure coated with precious metals that facilitates chemical reactions converting harmful emissions into less toxic compounds. MOSTPLUS uses high-density ceramic substrates with proper precious metal loading to meet EPA requirements. While we can’t verify the exact platinum, palladium, and rhodium ratios (proprietary information), our emissions testing confirmed these converters effectively reduce CO, NOx, and hydrocarbon emissions within acceptable parameters.

Heat-Resistant Construction Built to Last

We paid particular attention to the construction materials and welding quality. The stainless steel housing demonstrates solid craftsmanship with clean, penetrating welds that should withstand the thermal cycling these components endure. The heat shields are properly positioned and secured, providing essential protection to surrounding components and helping maintain optimal catalytic converter operating temperature (approximately 400-800°F for peak efficiency).

Complete Compatibility: Confirming Your Vehicle Fitment

This MOSTPLUS set is specifically engineered for the following vehicle applications:

• Chevrolet Silverado 1500: 2007-2013 (4.8L V8, 5.3L V8, 6.0L V8 engines)
• Chevrolet Tahoe: 2007-2013 (4.8L V8, 5.3L V8, 6.0L V8 engines)
• GMC Sierra 1500: 2007-2013 (4.8L V8, 5.3L V8, 6.0L V8 engines)
• GMC Yukon XL: 2007-2013 (5.3L V8, 6.0L V8 engines)

Critical Compatibility Note: These manifold converters replace the upstream (pre-catalytic converter) units mounted directly to the exhaust manifolds—NOT the downstream converters located further back in the exhaust system. We recommend verifying your specific failure codes and visual inspection to confirm you’re replacing the correct converters. The part numbers 674-522 (left/driver side) and 674-732 (right/passenger side) directly cross-reference to OEM specifications for these model years.

Always verify your vehicle’s VIN and existing part numbers before ordering. While this set covers the vast majority of standard configurations, certain specialty packages or modified vehicles may have variations.

Installation Insights: What to Expect During Replacement

Having performed the complete installation ourselves, we can provide realistic expectations about the process. This is decidedly an intermediate-to-advanced DIY project that requires specific tools and mechanical knowledge.

Required Tools and Materials

From our experience, you’ll need:

• Complete socket set including deep sockets (particularly 13mm, 15mm, and oxygen sensor sockets)
• Torque wrench for proper fastener tightening
• Penetrating oil (apply liberally to all fasteners 24 hours before starting)
• New exhaust manifold gaskets (highly recommended for proper sealing)
• Anti-seize compound for oxygen sensor threads
• Jack stands and wheel chocks (never work under a vehicle supported only by a jack)
• Safety equipment: gloves, safety glasses, and fire extinguisher nearby

Time Investment and Difficulty Assessment

For an experienced DIY mechanic with proper tools, expect 4-6 hours to complete both sides. If this is your first exhaust work or you’re dealing with severely rusted fasteners, plan for a full day. The driver’s side (left) converter typically presents more challenges due to space constraints with the steering components.

The most challenging aspects we encountered were:

• Seized fasteners: Manifold bolts exposed to years of heat cycles and road salt often resist removal. We snapped one stud even after penetrating oil treatment, requiring extraction—budget extra time for this possibility.
• Oxygen sensor removal: These sensors frequently seize in their bungs. A dedicated oxygen sensor socket and careful heat application may be necessary.
• Working space: Limited clearance requires patience and occasionally working by feel rather than sight.

Professional Installation Considerations

If you’re not mechanically inclined or lack the proper tools, professional installation is absolutely the wiser choice. Exhaust work involves hot components, potentially seized fasteners, and emissions-critical connections. Most independent shops quote 3-5 hours of labor for this job. Even with professional installation costs, you’re typically saving 50-60% compared to dealer pricing with OEM parts.

Performance and Emissions Results After Installation

The true test of any catalytic converter replacement is post-installation performance. We monitored several key metrics following installation on our test vehicle.

Check Engine Light Resolution

The P0420 (Bank 1) and P0430 (Bank 2) codes that initially prompted replacement cleared immediately after installation and the required drive cycle. These codes indicate catalyst system efficiency below threshold—exactly what failing converters produce. After 500 miles of mixed driving, no codes returned, confirming proper converter function.

Emissions Testing Compliance