Originally Posted by jmikes

I'd recommend adding a lightweight pulley to your modlist. It makes a decently big difference in how the car feels especially when you consider it only costs you maybe $200-$225 and is a relatively quick and easy install whether you do it or you have a shop do it. I like the Stillen standard performance / size one, but most brands will function and perform the same.

For numbers gain, people on here claim around 4-5 WHP and torque, although your torque drops off a little less after its peak and you end up with ~10 higher WTQ at redline versus stock pulley, which aint too shabby. I didn't get a chance to dyno the before/after of my install so rip

Dw about throwing off the harmonic balance, our engines are internally balanced and the pulley won't make a difference.