I would like to point out that the TPS codes indicate an open circuit at the TPS itself.
Also, the mention of unplugging the TPS with no change in the way the engine is running.
This sounds exactly like a TPS problem and TPS sensors are not too hard to test.
Check it:
http://easyautodiagnostics.com/ford_tps_test/ford_diagnose_tps_1.php
The test above is for a 4.6 or 5.4 BUT the LS V8 uses the same TPS as the Mustang 4.6.
All you need is a Multi-meter for checking voltage and continuity or just spend 30 dollars and replace the TPS from AutoZone.
DO NOT MODIFY THE IDLE IN ANY WAY. THERE IS MINIMAL PLAY ON THE FACTORY TPS SO THE NEW TPS CAN BE INSTALLED WITHOUT ADJUSTMENT IN MOST CASES.
Using the multi-meter, the TPS is easy to calibrate if you want to be certain of the below idle and WOT readings.
One last note. In my experience if you have a MAF sensor that is bad your car will likely not accelerate smoothly and/or idle at all.
Oil in the intake indicates a bad PCV.
A cracked intake is a troublesome part because the size of the crack could have drastic differences in idle and accelleration. Normally an intake leak will affect the idle first and it'll be higher than normal.
My 10 cents...