1999 Mustang Affordable Uprades - Two-Valve Bolt-Ons

On The Dyno
We took dyno readings immediately after installing each part and saw an interesting fluctuation in the rpm ranges where power/torque gains occurred, as well as the amount of gain and loss of each that the parts yielded. While the Flowmaster after-cat exhaust and AmericanMuscle.com-acquired pulleys boosted rear-wheel horsepower at the higher-rpm segment of a dyno pull (the pulleys proved to be the most productive individual element in our quintet), power gains were achieved roughly 325- to 330-rpm sooner once the BBK cold-air system, new 78mm throttle-body unit, and DiabloSport's plug-in PCM calibration were in place. It's also interesting to note the difference in horsepower and torque we saw when BBK's new throttle body/plenum setup was added.

The bottom line with this group of affordable Two-Valve pieces: Overall it delivered nearly 25 additional horsepower to the rear wheels and almost the same amount of torque lb-ft in a 100,000-mile tester burdened with an unfavorable (for dyno purposes) automatic transmission-and six catalytic converters. Hindsight obviously says that even with an AOD tranny, an off-road X-pipe also should be considered with this type of bolt-on upgrade.

This is something that Melvins...        read full caption This is something that Melvins need to store in their knowledge databases: Even though Ford did the right thing and upgraded '99 Mustang GT engines with Performance Improved cylinder heads, the company also saddled '99 GTs with six catalytic converters in the exhaust system. While we don't know the logic for that move, the multiple cats are huge restrictors that should be replaced with an X-shaped version with only two high-flow cats.

Since there's absolutely no...        read full caption Since there's absolutely no chance the stock exhaust will be reinstalled, Saul blazes through both tailpipes with a reciprocating saw and discards the mufflers once they've been removed.

The exhaust system bolts right...        read full caption The exhaust system bolts right into the stock location without issues. Flowmaster provides all of the necessary hardware (clamps, bolts, and so on) for this task, which Saul says can be accomplished in about two hours working at home by yourself using only a floor jack (and jackstands) to raise your Mustang.

However, based on the dyno numbers and the dramatic way in which the collection improved our '99 'Stang's driveability and street performance (see On the Street sidebar), we think it definitely earns a spot on the list of Two-Valve hop-up packages that will give any stock naturally aspirated, pump-gas New Edge a lot more get-up-and-go.

We're installing Flowmaster's...        read full caption We're installing Flowmaster's American Thunder post-cat exhaust system for '99-'04 Mustang GTs, Bullitts, and Mach 1s (PN 17312; $509.80) on our bone-stock 'Stang. The 21/2-inch system features two Super 40 Series mufflers and a pair of 3-inch stainless tailpipe tips that bring plenty of growl to a stock Pony's exhaust note.

The distance between the tip...        read full caption The distance between the tip of either index finger and the first knuckle joint is 1 inch. We used this distance as a positioning reference for the tailpipes, and secured the system when we were satisfied with the way things looked.

A good clean fit and great...        read full caption A good clean fit and great sound are the results of our first bolt-on in this test.