SL/R107: How can i make my 560sl faster?
In other words, you're pretty much screwed.
That's not that to say that it can't be done, but only with great expense and labor. Performance parts aren't readily available.
The simplest way to pull a few more HP and better mileage is to open up the exhaust. I had planned on replacing the stock system starting right after the O2 sensor with a Magnaflow cat converter and a Magnaflow muffler that at least looked stock, but with much better flow. I still have yet to do it - something always gets in the way. [new tires, etc]
I've pretty much come to grips with the fact that these are not performance sports cars, but very classy cruisers. I tried to autocross mine once and the understeer was...considerable. Running hard in 1st & 2nd gear was good for the CIS, though. The car ran great afterwards!
Good luck with yours.





