Warranty is also a concern for me as well. That's stopped me from jumping on the ECU tweaking bandwagon. There are a few tweakers who claim that their ECU mods can be made invisible from the dealership but nobody has actually tested it thoroughly and I'm not willing to be the guinea pig on that. There's options from GIAC to use a handheld unit to revert to stock mode supposedly undetectable and then there's the option of actually swapping out the ECU with a "backup" stock ECU when taken in for service but there's supposedly a backup ECU in the car that detects when the master ECU is removed. Where does it end? In the end, I decided to just stay with the stock tuning for now.

The RUF option is a good one albeit costly and their warranty isn't as long as the factory warranty so I'd wait until the length of the coverage overlaps before considering it.