Mods on a lease

I know that pretty much all of you that got an ST bought it instead of leasing it. I didn't really have a choice because I took my brother with me who is an expert at haggling sales people and that's why I got such a good price for mine. I would like to add some things such as wheels and a louder exhaust. I know people say as long as you can remove everything, it's ok. Is this true? I do plan on buying this car at the end of the lease (3 years) but I don't want to void the lease or anything if I take it to the dealership for service (not often)