Ordering a new ballast for 2011 bi xenon facelift model just looking for some advice on the difference. One ballast is H05 S0001 (which is the broken one i have currently) and the other is H04 S0002 both are oem the second option being cheaper also the second apprently being compatible with 8k0.941.597c (my car) just dont want to buy the wrong one or twice.