I own a LTZ400 and the other day I was messing around with the exhaust pipe and so i cut out the screen in the cap at the back of the pipe.....the bike sounds good and the high end is performing great....compared to my roommates stock version it seems to have an edge....here is the problem...when the rpm's drop down to approx idle speed the engine stalls....it is also running very rich....

this is very frustrating to me so i am seeking any advice anyone has to have...

 

Adjust your fuel mixture screw... and that should work....