What it does is to recirculate some portion of exhaust gases back into the intake stream (for cylinder dillution and cooling, to help smog numbers). It only does this however, under cruise or other light load situations. Other than cruise or light load it is deactivated.
If you decide to keep it intact, it really wont affect performance at all on a mild to moderate build up because of the conditions mentioned above.. If you want to remove it, simply get that function turned off in the chip you decide to go with.
I have all the pieces in place but it's turned off in my present chip. I kept everything intact because of the smog checks I used to get hit with out in Kalifornia.
