cars don't need backpressure to run good. it's an old myth. if you understand what backpressure is you would understand why getting rid of it is a good thing. do a quick google search, but skip the honda forums.

 

i was told a little is good too but i guess not

 

there's tons of topics explaining backpressure, i've made many posts about it myself. if you do a little searching through some older threads you'll learn what it is and why you don't want it.

to sum it up, basically it's air going the wrong way through the exhaust. which means the engine has to work harder to get the same amount of air out. that harder work = lost power. the idea in making more power is to make the engine more efficient. this is why a proper sized aftermarket exhaust usually gives some power gains, because the engine has to work less hard to get the air out.

there's more involved, but that's the simplified version.