They can't void your warranty cuz of the exhuast but my sis had the same problem with her acura CL

She happened to have warped rotors caused by driving with the e-brake applied.
When she applied the brakes, her steering wheel would wobble like crazy.

 

i used to slide on my stock tires all the time and after a while my wheel started to have shaky steering near 60mph. the reason why is i wore the tread on my front left down so bad i was losing chunks and steel braidings were showing. anyways, hope this helps.