[PawPaw271]

I am new here and I need help. I have a 1992 Chevy G30 based small motor home I have had for 20 years with regular maintenance and I have a problem I can't resolve.
The engine starts up ok, but when cold it will hardly run. Low idle, stumbling and no power. Here is a list of what I have done so far.
New plugs gapped at .035, new distributor cap & rotor, new plug wires, new ignition module, idle control, map sensor, vacuum lines, injectors, fuel pump and filter, fuel pressure regulator, oil pressure switch, fuel pump relay, knock sensor, TPS, pulse coil, EGR valve, EGR controller solenoid, ECM and coolant sensor/sender. I also drained all the gas and put in fresh one week ago.
Fuel pressure is at 12 PSI, timing set at 6 degrees BTDC and it is holding a good steady 22 inches of vacuum.
The compression is good and does seem to have jumped timing.
When you first start it up when cold it will never get to the cold start RPMs of about 1200 rpm that was normal for many years. It's only at about 550 rpm until it warms up and then only about 1000 rpms. When it's cold it also seem to be missing. It acts like low fuel pressure, but it shows good on the pressure tester.
One last thing. If I pinch close the fuel return line going to the fuel tank from the back of the TBI with a pair of needle nose the rpms will come up sometimes, like is is a low fuel pressure issue.
This is driving me nuts and I have worked on my own autos for over 50 years.
Any help or insight would be helpful.

Thank you,

Paw Paw