The way to do it is remove the old paint off then prime and repaint. Alot of places I know doesn't remove the old paint but just primes and repaint. You can get away with this direction but higher chance of paint chipping. I chose to repaint over the existing color since they guaranteed me of no chipping....And it saves me money as well. Oh yea, it was for my OEM lip spoiler so I didnt think I had to worry too much about chipping. Yours being a front splitter, you might have to worry about it more. It would be bad to have it chipped and then see the yellow color on an NFR showing. I guess, I would strip the old paint off in your case. Don't mind me, just trying to add my .02.

 

Thanks for the info. I was wondering if mugen front splitter sits lower or something. I'm not very sure why front splitter is more susceptible to chipping. Is splitter much lower than oem lip?