ran the 1/4 without than with the underdrive pulleys, to see a differance. I know that is the worst way to test that sort of thing. But just thought I would ask.

 

The UR UDP, full exhaust (hi flow cat and catback) with a 60mm TB dropped my ET 4 tenths and added 1.5mph. I did notice a difference with the UDP its slight but after time you notice the car has abit more pep. The only problem is that at idle with lights and AC on your voltage drops to battery level. If you don't turn off the lights or AC before turning off the engine you will run down your battery quicker.