AM I GOING TO BE ABLE TO FEEL A BIG DIFFERENCE WITH UNDERDRIVE PULLEYS???? AND IS THERE SOMETHING BETTER TO SPEND 200.00 ON??

 

With a car as heavy as a Mustang, you'd be hard pressed to feel any differences of any bolt-ons short of a full intake system revamp and an entirely new exhaust system. Although the gains are given, it's just that the car's too damned heavy for you to feel, and this is what causes a lotta people to get all pissed off at 'em and call them a waste of money.