Bit of a thread hijack, im currently considering the same sort of thing for my '05 636. I'll be doing all sorts of rides so it includes trackdays etc. and i'll be getting an air filter and piggyback ecu and getting it dynotuned.
i was wondering if anyone here actually has ever put a full system on their 636 or similar? what were the gains over just a slip-on? Sound, performance after tuning etc?
I'm currently considering the Akra or ARATA full system for ~$1200US or just the slip-ons for $450US. Quite a big cost difference. Anyone with any experience with these?