HELP NEEDED

As far as recommendation, since it would be a total custom build you're taking a big risk. For one, nobody has done it on our cars that we really know of, maybe someone has but there isn't really any data readily available showing how much of a difference it would make for us. And also, since you're doing it custom, you would have to really, really, really, really know what you're doing so you don't have problems.
A buddy of mine sent me a post from a Bimmer forum where a guy ran meth on his 335i, although a very rare horror story occurrence, he basically blew his engine up.
A lot of BMW guys run it on their cars. A couple threads with pros/cons
http://www.e90post.com/forums/showthread.php?t=478943
http://www.e90post.com/forums/showthread.php?t=566589
Here is the one of the engine failure, it gives me chills to think about this happening: http://www.e90post.com/forums/showthread.php?t=807663
I looked into meth injection and will eventually add it but (I think) its going to require an ECU such as an AEM unit where you can set it all up to get maximum gains.
http://forums.viperclub.org/threads/...It-works-great....
http://kennedysdynotune.com/custom-water-injection/
Which pulley? Crank or underdrive? I have both. They both help
air intake such as needswings or renntech
TCU tune helps tighten up the shifts
You can add gears but do that before the TCU tune and then the TCU tune can adjust for it.
Weight reduction: lightweight battery, racing seats, carbon hood, fenders, rear seat delete
Nitrous.... there are threads, C55, CLK55, SLK55, cant remember with a great write up and pictures. 100 shot. C55 on dragtimes went low 12's on dragradials


