I'm not going to point the finger at anybody but there is a lot of bad info in this thread concerning the operation of the EFI system without the cat and rear O2 sensor. Bottom line is the motor will run perfectly fine without a cat as long as the front O2 sensor/s are in the exhaust and connected, the rear sensor has zero effect on engine operation it's just there to monitor catalytic effectiveness and trigger the CE light if the cat deteriorates, in other words it's a smog nanny. The rear sensor can also be replaced with an O2 simulator which should keep the CE light off.
For the record I don't condone removing the catalytic system, universal cats sized for this truck are cheap and can be swapped in relatively easily in most cases.. though some apps will require welding.