1999 passat 1.8L turbo - "hesitation" when accelorating

As above, i have a 1999 passat, 1.8L turbo, auto, approx. 92500 km. It has issues with acceloration. If i have to punch the gas, it stumbles badly and almost seems to want to back-fire. This is even worse when going uphill. It drives fine otherwise, however when i need to demand a little more, it stumbles so bad sometimes that the car seems to lurch. I have taken it to 3 different mechanics' and they cannot determine what the problem is. Finally took it to a dealership and they said a component in the turbo was jammed (the rod) and they were not able to "un-jam" it. That was causing the turbo to be "active" all the time... SO...I have recently changed the turbo (oil, oil filter and coolant included), the MAF, the pre/front O2 sensor, the fuel system seems to be good when we did a pressure check, as with the vacuum lines. I've "wiggled" the wires under the dash going to the vehicle computer. I've changed the air filter. I only use premium (94 octane) gas. And now i am at a loss.
I have an OBD scanner. Previous codes have been: P1555 - "turbocharger boost pressure control valve, upper limit exceeded"; P1196 - "O2S heater circuit bank 1 sensor 1 electrical malfunction"; P0103 - "mass or volume air flow circuit high input". I have been unable to produce additional codes, even though the problem persists...
:angryfire:banghead::aargh4::alcoholic
Please, please!??!?!?!? Anything would help!!! I love my car, but lately i just want to drive it off a cliff!!!! If there's any questions anyone might have, i'm not very "car-smart" but i'll do my best to answer!
Many Thanks!

I might help if you post your engine code. I would clear all fault codes and get a proper vag-com scan. OBD scanners are not very good and they are at their worst with early models.

Thank-you Martin1810,
Engine code is "AEB". I have cleared all the codes, though i have print-outs of all of them. This OBD scanner (model 3120) is all i have unless i want to pay $150 CAN to a dealership to use theirs. Thankyou for the advice though - i'll keep that under consideration when i scan my car with the OBD.

It is possible your OBD scanner is giving you duff info. P1555 can be translated to 17963 throttle valve control fault. eg. - Voltage supply or earth for throttle valve potentiometer (G69) and sender for throttle valve positioner (G127) defective
- Open circuit in the signal wire for G69 and G127
- G69 and G127 defective
- Positioner mechanics or throttle valve tight or sticking
Try giving the throttle valve assembly a good clean. It might be just sticking.

Thankyou so much! I'll try that this weekend! Hopefully this will be the last fix for this problem!
How did you get that other code?

The code comes from VW's own data. That's the problem with the early days of OBD. I can't guarantee I am correct but that code fits your symptoms and that's the code VW say you should have from that OBD code. good luck.