motor shaking at low regime (cold and warm motor)

Hi ,

I have a Jetta 2001 , GLS 1.8 T (180 000 km)
I had a check engine since few months. I scanned the motor and I had these codes:

P0102: mass air flow circuit G70 :low input
P0300: randow / multiple cyclinder misfire
P0301 : cylinder / misfire
P1297 : connection charger to throttle valve pressure dropped !
P1137 : Bank / mixture adaptation (add) system too rich !

The problem is that the consumption becomes high (15l / 100 km) !!! Besides , the motor is shaking when the regime is low (7ooo rpm) !!! the needle giving the rpm shakes then the motor stops !!! I think the motor is not getting enough air .. But I don’t now what is the reason : the throttle valve , the oxygen sensor , the filters or electronic problem !!

I’m afraid it will cost me a lot of money if I go to the dealer .. any one has any suggestion or idea what can I do ?
I will keep you informed,
Thanks,

My Jetta is only a 90, and doesnt have the OBD-II codes like yours does, so this is a feeble guess:
If your car has a large rubber duct running from the air cleaner up to the throttle body, then check that it has no rips or tears and isnt loose. The mass air flow sensor on the older Jettas was by the air cleaner, and I think it still is. That is what tells the computer how much air was coming in. If there is a hole in that rubber duct, extra air would get in, that the mass air flow sensor was not seeing, and the engine would be running lean (too much air, not enough fuel). This would cause misfiring and a rough idle. The misfiring could result in enough unburned fuel going out the exhaust for it to be sensing that its running too rich.