Amazon.com: Red Line 60103 SI-1 Fuel System Cleaner - 15 oz.: Automotive
TRY IT. My car has made a full recovery as result of this stuff. I still get a *slight* hesitation when I gas it, but otherwise is runnig well.
Those idle air hoses do help, make shure you buy genuine mercedes ones. The aftermarket ones are garbage, and wont fit.