Engine stumbling problem

[Sidewinder600]

Hey all, I'm having an issue that's a little different than the regular crappy acceleration/stumbling problem. I just replaced my MAS and everything was alright for the first 100 miles or so. Now it does this thing where it starts a little rough (though not nearly as bad as with the old sensor) and it will idle rough for a minute or two if I'm not driving it.
That doesn't really bother me as much since it's still a huge improvement over the old sensor, but the bigger problem is if i start driving within the first minute or two of starting when it's cold, it feels like the throttle actually cuts out on occasion. I'll keep a steady throttle and it'll buck around like I'm chopping the gas on and off. If it's right after I start, it'll make it look like I'm learning to drive manual for the first time, and if it's warmed up for a minute or two it'll only do it two or three times. Either way, within a minute of driving it's gone and it runs great.
One thing I should add: when I got the new MAS, I only got the insert (the electronic part), not the whole big housing tube thing, and just put it in the old housing. I was careful to get a genuine Bosch sensor since last time I tried a cheaper generic one off ebay and it make it run like shite and just made the CEL come back on... :mad:
Anyway, any ideas?

[Sidewinder600]

Oh yeah, should probably mention it's a 99 C230K...

[xvvvz]

FWIW, I have been trying to overcome some sluggishness problems when my 99 C230k is first started up. My problem doesn't sound like it was nearly as extreme as yours but the car had a dead spot in acceleration when your first drove off in the morning(accelerate a slight bit, dead spot, then catches up on acceleration) and then it ran a bit off/irratic for a few blocks (like it wasn't adjusting the fuel mixture right). Also, every once in a while the transmission was making some odd shifts.

I thought it was the MAF for sure (and am still wondering if there isn't something intermittant going on that they can't see during their test) but the tech insisted the MAF was just fine. The first obvious issue he found was a split vacuum line coming off the supercharger which I hadn't seen. If you haven't checked all of your vacuum lines for the engine, I would start there (check at the connections and then carefully all along the tube itself). Also make sure the air filter box if fully seated and that you reseated the MAF correctly so there are no leaks in that whole air delivery tubing system. The final thing the tech did was to install a new ECU/control unit. My tech said he came across a tech bulletin that mentioned this as a cure for the problems I was describing. He checked my unit's number vs. the updated one and found I had the older version. I just got the car back a few days ago and have barely driven it at all. Therefore, I have not driven it enough to be able to tell for certain if it did anything.

Let us know if and how you solve your car's issue.