It may seem crazy, but eventually I plan to set up a twin turbo on this engine. In the mean time, I'd like to add a little bit without changing the engine entirely. Such as:
#1 bigger exhaust (custom-made manifolds and the like)
#2 euro cams (or something made to run a little more HP)
#3 tighten-up the transmission (or convert to first gear start)

I realize that running a larger exhaust will lead to more HP, less fuel economy, louder sound, and take alot of time ad work to implement, but it's only a small part of a much larger project...

Euro cams are an option because I don't know of anyone who makes custom cams for these engines. As far as I understand, different cams change the whole performance curve (allowable octane ratings, compression timing, efficiency at different RPMs, and emissions) I guess what I want to know is did Mercedes make any cam [compatible with my m117] that would work better than my stock for turbo charging purposes?

As it stands now, the transmission shifts fairly hard (partly because I'm idling too high) and the kickdown works perfectly stock... I'd just like it to be more adjustable, maybe set it up for first gear start...

All of this change is a precursor for my greatest change in the engine... My custom-made engine management system. Once it's done, I plan to have a fuel-injected and twin turbocharged rubber-burnin' fireball of German engineering My management system will take measurements from 15+ thermometers, pressure sensors, absolute rotational position sensors, and 8 oxygen sensors. Then use that information to control the spark timing, air-flow of each cylinder, gear shifting, and fuel-injection of all three grades of gas, ethanol, propane and hydrogen. Once completed, I'll have probably have the most advanced engine management system in existence... But until then, any advice towards the three possibilities list above would be greatly appreciated.

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iThink Different
Building an all new electrical system in my
1985 500SEL