can I change my TPS myself?

if you don't know how to set the tps then you need a shop to do it. but thanks to the internet you don't need to take it to a shop for something so simple..

http://www.muscularmustangs.com/tps.php

the tps is not adjustable on our cars, is it? the computer reads the value when it starts up and then uses that as its reference point.

The mechanic that told you that wants your money. Do it yourself...like said above our's is non-adjustable

You followed the very good advice above and got it installed already, right?

5 minutes well spent.

The TPS is held on with 3 screws and is a direct swap. The TPS will only go in one location. The only adjustment to the TPS is via the set screw on the throttle body opposite the TPS. Some people mistakenly use this to set the idle speed instead of the idle bypass screw.

In addition: There's a ratcheting function, which means the puter continuously checks the lowest reading the TPS reports. It uses this to set the baseline. So as long as the TPS is somewhere in the rough range of ~0.80 Volts to 1.20 Volts, it will 'zero' itself out (this is the adaptive ability of the EEC. This is built into the computer code to accomodate the range of sensor tolerances seen on the assmebly line).
And if the range is above that threshold, it should set a code. If and when it sets a code, that's the time to consider modification of the sensor mount to change the reading.

Now if you really wanna' start hosing with it, as long as you don't break anything (I think Grady discussed that possibility on this or the other current TPS thread), I *personally* don't have an issue with guys screwing with the TPS if it makes them feel better.

FWIW (point of comparison), mine sits at 1.19 volts (static) and seems to do fine.

Good luck.