i was wondering how big of a rim i can use with out getting my ecu reprogrammed i am runnung 14teens now

 

The size of the wheel isn't the issue. The overall diameter of your tires are what you want to keep close to the stock size unless you get the new tire size entered in your ECU. If you have an LS, your stock tires are pretty small and leave a huge wheel gap. I would try to find a wheel you like and then find the appropriate sized tire that has a diameter of 25"-25.5". Here is a handy tool to help you compare your stock tire size to low profile tires. http://www.rims-n-tires.com/rt_specs.jsp

If you're too lazy to do some research (lol), I would recommend an 18"x7.5" or 8" wide wheel with 225/40/18 tires. They have a 25.1" OD.