1994jettahelllllp!

Hi all.
I have a 1994 jetta3 made in mexico and it is having a terrible problem.
It will start ok and idle ok it will drive in reverse but when it is pulled down into drive the rpm's drop way down and it will hardly move even if you go all the way to the floor on the pedal.The check engine light is on and it had code's for iac and throttle position sensor but they both check out ok if you test them by the method given in mitchell on demand instructions for testing sensors.I have SNAPON MODIS and I checked them on the datastream readout and the are within parameter's.
I have very little experience with vw and i took this as a favor to a freind.Now I can't get rid of the car and because i have little exp with them i am at a loss.I would like to get this girl back her car and she doesn't have a lot of money as she is a freind of my daughter and they are both student's with little money to spend any help would be greatly appreceiated

Will the engine rev in neutral also? If it's fine in reverse, but dies out when accelerating in drive, I'd look at the wiring connections where the harness goes between the engine & body. I'd particulalrly look at the connections & wiring for the IAC & TPS, because it sounds like when the engine torques from being put in drive it's pulling some wires, setting the codes. It may be putting torque on the harness in the drive position, breaking a weak electrical connection or bad wire. I had a Caravan do this to me once.