I have a 2006 Audi A4 that has no passing power. When I step on the accelerator the car will shift down into a lower gear , rev about 3500 RPMs but will not shift up again until you let off the accelerator. I have replaced the HPFP sensor and the Mass air flow sensor but neither has changed the performance.

It is a 2.0T 4 cylinder, yes it is an automatic with the tiptronic transmission.
When it revs to 3500 RPM, the speed is not increasing it just revs until you let off of the accelerator and then it will gradually get to the speed you want as long as you do not cause it to drop into the passing gear again.

I suspect that it is a sensor somewhere.

Any constructive feedback would be appreciated.