I know this sounds funny but check the wiring harness that runs from the carb to the emissions box located on the driver side fender. One harness has 8 wires, the other 7. Make sure there hooked up to the right pig tail as they both will mate up. During the rebuild process I made this simple mistake and a lot of what your explaining sounds eerily familiar...

Proud owner or driver of a 1989 Mitsubishi Mighty Max 4X4, 1989 Mitsubishi Montero SWB, 2008 Mitsubishi Endeavor, 2008 Mitsubishi Eclipse SE, 2007 Galant.