improvement on the piso, but still confusing

[Low87]

First off, many, many thanks to Mike for being the kind of guy he is! He sent me a used but working idle air control valve, MAP sensor, throttle position sensor, and O2 sensor, on his dime!
I got them today, and swapped out everything but the O2 sensor (don't have one, remember?). The truck started right up and idled fine. It kept going without dying like it should have already. I got my hopes up, closed the hood, and pulled out of the driveway. I got to the stopsign 50 yards from my house and it died like old times. Started up, off I went. Another 100 yards, another stop sign, and it died again. Another 100 yards, slowed for a curve, it died again, a little harder to get started this time. Another 50 yards it died at another stop sign, took about 5 cranks to get it going, had to keep pumping the gas to keep it running and use the brake to control speed. Pulling into my driveway, it died again. Got it started again in the driveway, idled smooth and without dying. It kept going, so I started playing with the gas. I could pump it to the floor with no problem. Slowly pressing down on the gas almost caused it to die, but it didn't. I sat in the driveway letting it idle, pumping it, revving it, flooring it, and it ran fine. WHAT IS GOING ON WITH MY PISO ENGINE???? Tomorrow I may nurse it over to the mechanic's a mile away, mostly neighborhood and industrial park streets. If someone can help me out before then I'd sure like to save the $.
THANKS AGAIN MIKE!