on rave its known as the 900s, on idle sometimes the engine starts to shake then idles ok again before doing it again. mine did the same thing until recently when i had to change the engine ecu to to a fault, with the new one i aint had the problem back. apparently its a software issue that they only seemed to fix on the last models so when you order a new one they send the latest version and job done. not bad a, only costs 500 quid for that.:jaw