Thanks all. I am running Marks chip in my 535 and love it. This car is a daily driver with mostly freeway driving. The 535 runs strong & smooth. I sure feels quick but maybe not as quick as it really is. But I sure like it. The M5 I drove for only a short time. Maybe as someone said I need more time behind the wheel. The big difference was it was not as smooth at. Is the M5 motor as smooth running motor as the 535?