Oldsmobile/Buick Repair: 1988 Cutlass Calais intermitent rough idle and engine service light, torque converter clutch, throttle position sensor

Question
We have replaced the computer, EGR valve, Throttle position sensor, but have not fixed the problem.  
We have had it in the shop numerous times and no luck.  Failure code continues to come up as the Throttle Position sensor.  I checked the voltage according to the chiltons manual and it is good for the full movement of the throttle.

At times it will run perfect but in most cases it idles rough and stalls when in gear.  When in nutural, it idles o.k.  If I stop at a light, usually cuts off. Restarts fine.   any ideas?

Answer
Check the vacuum, and check the brake master cylinder for vacuum leak.
Then check the temperature sensor. Read this link.
http://www.chevytalk.org/threads/showthreaded.php?Cat=0&Number=1366279

Did the throttle position voltage move smoothly from about 5 volts at one extreme, to about half a volt....consistently?

And I have heard of the transmission TCC, torque converter clutch solenoid valve sticking, and keeping the torque converter clutch partly or completely locked up. That would explain the runs good in neutral statement.
Try Google search for TCC, or torque converter clutch.

Van