I personally have not used 99mpower but he's the only other guy that Brandon Watson will let work on his car so that speaks volumes for me. If I wasn't still under warranty, I'd use 99mpower for sure.
Oh and if you don't know who Brandon is, he's just a kid with over 15,000 track miles under his belt and is kinda fast... so his car has to work well under a lot of abuse.
2016 F82 ZCP / 6MT / SSR Intake / Volk ZE40 18x9.5 et20 & 18x11 et34
Toyo R888 265/35 & 305/35 / Macht Schnell Sport Competition Springs