I have a 2003 MC stick, in first gear on start I accelerate through 3500 Rpm and something slips, it feels like I lose the accelerator to the floor, as if the engine hangs up, lasts just long enough to scare me. Only in first gear and only from a complete stop. I have 2500 miles logged, happens everyother day. Mentioned to service they looked at me real funny, no explanation! Also when the AC is on I get a chug or sluggish idle just below 1000 Rpm.

 

You need the ECU software upgrade 33.1, which is the second upgrade since 2002 to deal with your problem. I had the same exact thing and I am okay now....car runs perfect....... :smile:

 

Could it be the ASC or DSC? In wet weather or if you rev the engine up before letting out the clutch you may be slipping your wheels. The traction control system (present in both the ASC and DSC) detect a slip in the wheels and sortof kill your power until the traction comes back. Just a thought.
-Chris