[200q20v] Low Boost Puzzle - Help needed

[Steve Bednarski]

I should be receiving the VAG-COM software soon from Uwe Ross at Ross-Tech
and was encouraged by preliminary testing on my 1991 200Q Avant.  I will
post more details after I receive the software

I would like to hone in on the following:  My boost pressure on the car
reaches a maximum of 1.5 Bar on the gauge.  I believe that the gauge is
correct as the car does not feel as fast as the prior 1991 I have owned.  It
is barely faster than my 1990 10V 200Q.

Here are some key additional details:

1. All output checks work and the WGFV clicks during this test.
2. A fault code for the speed sensor is the only one that appears.
3. All hoses seem to be in fine shape with no evidence of cracking on this
low mileage (59,000 mi.) car
4. New plugs, oxygen sensor, and distributor cap have been installed.  The
distributor rotor was fine and not replaced.
5. Highway fuel mileage is 24mpg at 65mph (which seems a little low)
6. Car runs and idles smoothly.

Where should I look in order of priority for my low boost problem?  Can I
still have a defective throttle potentiometer, for example, but not have it
show up in the fault codes?

Any help would be appreciated.

Steve B.