I've just recently updated my 2000 M5 vanos system with the later gears and springs. While in there I had the chain rails and a few other parts replaced. I drove it for about 500 miles and then the SES light came on and it was running rough as it appeared to be out of time at low RPMs it really struggled. After further investigation, the car runs great until the thermostat opens (checked via the Bavarian Technic software). As soon as it gets to temp and the thermostat opens, it starts running poorly and throws a 185 Vanos regulation bank 1 error. Today we pulled the circuit boards and tested all of the solenoids and all of them are working fine, so I'm not sure what else it could be. I'd appreciate any input. I'm just really confused by the fact that it runs great until it gets to temp. Thanks!!