I've seriously thought about it, it fits! Just not sure on mk5 immobilser the systems changed from Mk 4's , might be the whole transfer of loom ect..... I'm leaving enough room in my Mk 1 for one, but I'm not going to be the first (lack of time & spare money!) it's a cracking engine out of the box, could produce so much more power (talking 140 without DPF) if it wasn't so restricted of air if anyones thinking of it, get one out of a golf, not a passat- there a slightly more secure & more relaint on CAN-BUS systems