If you're getting 39 PSI of fuel pressure at idle instead of 31, you will have a low idle.
TPS should be 17 or less. Sort the fuel pressure stuff next.
And, Renix doesn't learn TPS adjustment. The ECM sees exactly what the MT 2500 does.
I just checked an 88 Owner's Manual.
Same procedure as 91 and later. Being as there is no mention of the vehicle having a limited slip, or any cautions, I'd say you're good to go.
So, it turns over and starts? Then dies quickly?
If so, it might be a bad fuel pump ballast resistor. You can bypass it for testing purposes and see what happens.