2000 Passat 20V tiptronic gear hunting & surging

I have recently bought a 2000 Passat 20V tiptronic. When in Drive and I have my foot on the brake eg stopped at the lights, the car surges, as if it wants to select a higher gear. When driving in automatic, the car seems to be hunting for a gear regularly. I have taken it to the VW dealer and there are no error codes coming up. Can someone please help. Thanks

i notice v6 autos shift weird compared to 1.8t auto.

I managed the get the surging fixed. I took it to a different mechanic who said that there were a couple of error codes in the system, which he didn't write down! As far as the gear hunting goes, it's still doing it and the mechanic could not work out what it was, if you have any insight that would be great. It only seems to do it between 4th and 5th in automode ie not sure which gear to pick. I spoke to a mechanic friend of mine and he said that since no error codes are coming up, it could be anything. From his perspective, it sounds like the throttle position sensor. Is there any way of resetting it without having to pull it apart? Thanks again for the feedback.

try turning the key on and slowly depressing the gas pedal to the floor all the way and then letting off slowly a couple times. Technically you need to adapt the throttle body with a scanner. Is your passenger front floor wet at all?

We can rule the throttle position sensor out! I tried turning the key on etc and it seems to improve it for a short time, but it comes back. I did come across someone with a similar problem in another thread and the transmission control module was what was wrong - it needed to be reflashed/reprogrammed, but didn't fix the problem fully. If you can think of anything else let me know, but I will have to take the car to the dealer to get the TCM reflashed (whatever that means!). Again, thanks for your help.