Why are they there? What do they do exactly...has anyone removed them?

 

From what I can tell based on the stock exhaust, the resonators are there to help eliminate the raspy sounds in the higher RPM ranges.

I have B&B exhaust, which has no resonators, and when I get up around 5k rpms and up, my exhaust has a definite rasp to it.

I got to FINALLY hear TXSTYLE's Borla over the weekend, and trust me, you don't need to change a thing with that exhaust. It sounds INCREDIBLE!!!

 

like what 350zSpeedRacer said, it helps to produce the lower exhaust tone, and if you remove them, the exhaust will sound raspy. Not many people like them. Not sure if you will gain any hp from it.

You will have to fabricate two straight pipes to replace the Borla resonators, since there are two of them.. It will probably cost you around $100~

 

I don't think it would be worth it because it will ruin the sound and the gains would be minimal. I removed the silencer on my stock exhaust and I want to put it back on because of the sound that it has now.