Originally Posted by sapph1

When it's activated, it does affect the way the engine runs and how the car drives, the idle become very rough and the revs drop, also i found that the car wasnt nice to drive at low revs but thats not what it was designed for, it meant to be used when changing gear at high revs. It does sound strange that it works when the engine's cold though, best thing would be to contact msd i would say.