Tomorrow my mechanic friend is Coming home. Hes gonna run couple test, plus were Gonna check if the shelby pump are correctly connected to the gt harness like you mentionned moose! Since it
Throw two illogical opposite code, your explication make sens, if it does fix the gas gauge and remove the code, im throwing you some money on paypal sir!

 

edit wrong thread ****

 

Interesting idea, I had to google it. Not sure it will tell you anything that a regular compression wouldn't.

 

All i can say is this don't sound bueno at ALL.

I have no idea what it is with the things you have tried to fix.