Is he running his ballast directly off the factory head light wire harness? Or is he running them through a 30 amp relay? Some HID ballast's require a pretty large current draw in start up. Not sure if this is the case with your friends HID set up, but you may want to check. If he is running them directly off the factory harness, I would recommend running them through a 30amp Bosch relay. Also he may want to check and see if he hooked his ground wire up to a factory ground location and disturbed a factory ground.
Just suggestions.
Just suggestions.