2004 Chevrolet Avalanche - Pac It In - Tech

The custom programming is the final step, providing the engine with the tuning it needs to take advantage of the other modifications. The fuel and spark advance curves are optimized for performance, and the factory delay in the power-enrichment function that occurs at wide-open throttle is eliminated. "When it's floored," Reese told us, "You get the full thing." One thing the programming doesn't do, before you ask, is remove the factory 100-mph speed limiter, and for good reason. When SLP tried it, our source reports, the factory driveshaft yoke broke-and violently expelled the shaft. You've been warned.

So, what did the PerformancePac do for our subject Avalanche? Making our dyno pulls in Second gear to avoid that pesky speed limiter, we picked up 33 hp and 26 lb-ft of torque. Had we been able to make our runs in Third gear, we undoubtedly would have registered greater gains, a supposition backed up by the Avalanche owner's subjective observations. "I didn't think it was underpowered before," he reports. "But I can really feel the extra power."

And from the "have your cake and eat it too" department, our subject's owner reports that the much-improved growl coming from the new exhaust system isn't overly loud. On top of that he's getting better gas mileage-another feature SLP engineered into the equation. Check out how this one-stop shopping trip added to this daily driver's fun factor. CHP