One of my friends told me that by getting a y-pipe or underdrive pulley, it would decrease my mpg. I kinda don't believe in him cuz .5 the time he doesn't know crap about cars (he drives a saturn with exhuast and intake: slow). So I want to confirm it w/ u guys. If he's right then he'll get my props.

 

Adding those mods will increase your gas mileage. they make the entire engine more efficient by reducing restrictions that the engine must work against.

But, you'll probably drive harder, so that will cost your MPG

 

thanx for clearifying
another dumb comment from my friend again. I dunno where I met this guy
How much hp or tq will the pulley help?