I had a ProBitz on my F10 520 auto. It was more aggressive from a standing start and I very rarely used the sports gearbox setting with it. Have used these in a few different cars with no problems. I did about 4K miles with this on the F10 and then suffered a high pressure fuel pump failure. It's probably not linked but have not put tuner box back on as it's due a service. No errors showed up on the BMW diagnostics re:tuner box so they won't know you had one fitted. I am putting mine back on after the service as the cars more fun. My wife drove the car after the fuel pump was replaced and said the car feels dead compared to before. She did not know it had a tuner box prior.
=andyk500;10789042]I've been looking at getting a power upgrade on my 520d and have looked at the plug-in system from Chipexpress. Power up from 181bhp to 224bhp, cost £395. I like the fact it's plugable and removable as I have a company car and shouldn\'t really do it.
http://www.chipexpress.com/products/2808/
Has anyone used this or can recommend an alternative. Comments appreciated thanks.[/QUOTE]