I am planning on getting a set of aftermarket 20" rims for my '07 LTZ (stock 20's are ugly and the chrome are too expensive), so I was wondering if the GM dealer would install them to ensure that the TPMS works after the exchange. I also thought about getting a little larger tire, 285/50/20 which I assume will affect the TPMS. Any suggestions? I am in the middle of researching this and would like to make a final decision soon.