Golf IV / Jetta IV :: Engine Dies At Startup / Codes For Camshaft Position Sensor

I've got a 2003 Jetta Wolfsberg that is acting up, I'll do my best to describe and outline the steps I've taken with the mechanic to fix the problem,

Occasionally, when starting the car one of two things happens, (1) engine turns over, fires, and then dies. Removing the key, letting the car sit for 30 seconds and trying again usually gets the car started. (2) The car will start but will run VERY roughly (misfiring, sounding like the engine is choking out). Very much like this (only sometimes much worse, usually ending in a stall): [URL] ....

Turning the car off, removing the key, letting it sit, and then trying it again will eventually work, even though it might take a few cycles. Once the car gets running it almost always runs fine from thereon. (There have been a couple occasions where the car has gone into limp mode, even on the freeway. Pulling over, letting it sit, and starting it again almost always fixes the problem. I've not yet been stranded.)

Diagnosis & Steps taken:

I get regular codes for the camshaft position sensor and also for the MAP (Barometric pressure) sensor. Both have been replaced.The MAP sensor and the atmospheric pressure readings are off by about 30 (something like 960 and 990). My mechanic thought that maybe it was an electrical problem, he noted that the two sensors mentioned above share a common ground. He replaced the ground because it looked corroded. This brought the pressure numbers both to 990 and the car ran perfectly for a few weeks.One thought was to splice in a new wire to the MAP sensor, to see whether it was a signal problem, this hasn't been done yet. Another possibility was that there is a problem with the ECM.

I THINK, that the problems began just after having the computer flashed at the dealership two years ago. I'd got a code about an update and so the dealership did this. I don't know whether this could have had any effect on these problems, but the times lined up too well to not mention it.