On a stock engine, how much? i'm talking 1 5/8ths equal BBK headers, off road h-pipe, and flowmasters...20hp? Most Stangs i seen dyno @ around 190hp to the rear wheels, so i would dyno at 210? thanks
That is about right. If going from a completely stock exhaust system to a set of headers, 2 1/2" X or H pipe, and high-flow mufflers/cat back, then expect about a 10% increase (roughly 20 HP) in top end horsepower. Just be aware that you may loose a bit of low end around town.