I just had my 1999 Mustang
Gt done with a BBK 78 mm throttle body,BBK side fender well cold air intake,BBK long tube headers into a Flowmaster 3 chamber cat back system, and a dyno tune from Alternative Auto in Chesterfield Mighigan. I got 266 rear wheel hp on a hot humid day. The car has 74,000 miles on it,hope this helps you!!!