The white ’99 Silverado was beginning to show the wear and tear of fighting the highway wars the last few years. The once proud and pampered show truck—a standard cab  shortbed with matching cab-high camper shell—hadn’t spent much time in daily service until recent years, but now it bore its share of dings, dents and scratches. It was obvious that the 50,000 miles on the odometer hadn’t done the 5.3-liter V-8 much good. Part of the reason for the dissipated performance was the exhaust system, a very tired, less-than-top-quality aftermarket after-cat that had started banging, squeaking and leaking.

Installing a new after-cat from MagnaFlow was at the top of this owner’s agenda. He acquired a MagnaFlow (part No. 15617) polished stainless steel aftercat performance system for his Chevy, and because he’s in the automotive business and has a lift at his own facility, all he had to do was enlist the help of a colleague experienced in exhaust system installs to lend a hand with the hookup.

Both after-cat systems—the old aftermarket system previously installed in the Silverado and the new MagnaFlow system—are mandrel bent, which means that the tubing is the same diameter and configuration throughout. For cost and speed of manufacturing reasons, original factory systems are, for the most part, press bent. This means that the tubing is slightly distorted (pinched) in places along the bend. These cheaper, press-bent factory systems do not do as effective a job of evacuating exhaust gases, which is why aftermarket systems such as the MagnaFlow are known to produce a little more power, depending upon the system and application. In addition, the MagnaFlow system, advertised as a “straight-through” performance exhaust, is devoid of restrictive baffles in the muffler.

The reported performance level of a stock ’99 5.3-liter Silverado is about 228 hp. With an aftermarket system like the one removed here, the Silverado would likely produce 230-236 hp, while the MagnaFlow system is claimed to produce 240-248 hp. You might also expect some advantage with the MagnaFlow system in fuel mileage—perhaps up to a mile per gallon, if driven accordingly. While we did not test these results, any decrease in backpressure is a move in the right direction.

Installing the MagnaFlow system in this Silverado proved to be a quick, straightforward install. The accompanying photos show those highlights.