Does anyone know the cheapest place to order the cat back system for the 3 on the internet? Also if i put this on is it going to void my warranty?

 

usually whenever you modify or upgrade your car it is going to void the warrany on the parts that you have upgraded. such as if you upgrade the exhaust...it will not be covered under warranty, but you sound system, lights, body, drivetrain and such will still be. so just becareful.