Hi everyone I bought an 07 Cooper s about three months, I am really loving it and I've been looking into tuning it now I hear a lot of people recommending manic tuning I wanna do the stage 2 tune and want to know exactly what I need and what everyone runs on their minis and where you all usually buy your upgrades. Would really appreciate the help.

 

For stage 2, you need a larger FMIC and a decatted or highflow downpipe.
Lots of choices for an FMIC. Forge, Helix, Wagner, these are the more popular ones.
For a downpipe, theres the Akrapovic (100cell), Milltek (decat or 200-cell), iPE (200cell), Mario (decat), WMW (decat). Theres plenty more out there.
Cat-back exhaust is optional. You can get an aftermarket intake, but it is not necessary. A high-flow panel filter (from afe, k&n, etc) will do just fine. It is also recommended that you get colder spark plugs. Many people run the evo10 plugs (NGK ILRK8E6).
You can get these parts from a lot of the vendors on this site.

Seeing that you have an 07, you probably want to do a walnut blast to clean up the carbon on the valves, if it hasn't been done already.