code 51/ quits when returning to idle

[cre]

The lamp you describe is the 'low coolant' light. The sensor is in the reservoir... not really the best indicator if the whole system is low, but it's better than nothing.

Code 41 mean there is an actual short or a break in the circuit. While the TPS being 'out of whack' shouldn't cause significant drive-ability or operation issues a short most likely will. A removed TPS will create rough transitioning when abruptly revving the engine, transitioning to idle and may affect WOT performance at lower loads; Smooth transitions in throttle shouldn't really see rough operation. This code will set and remain stored if the TPS is unplugged... Are you still getting this code after a reset? (Without looking at my notes I believe) TPS signal (VTA) should read >480mV at full stop (closed throttle) and ~3.48V at WOT.

You could install a universal unit but you'll probably need to add a separate IDL switch and you'll also need to verify that it provides the voltage as detailed above and not a 0V to 5V signal... On top of adapting it to physically connect you'll want to consider that when deciding if it's worth it. I rather like converting over to more readily-available and common components on rarer vehicles... like GM knock sensors.

Is the harness unmodified or has it been modified or shortened/lengthened at all?

Check your grounds, specifically E1 and E2. Also check Vc (should be ~4.8V at the TPS and AFM harness connectors with the ignition on or the engine running).