454 TBI swap from refrigerated box truck, timing problems I can't figure out

[yellowsnow]

I can't figure it out. My research has led me here.

It is a gen V 454 TBI from a refrigerated box truck manual trans, 1227747 ECM (no knock sensor or ESC could be found) . I put it in a 1988 C1500 with a turbo 400 trans. Picture album of build http://imgur.com/a/6VPoZ

When I unhook the timing bypass wire and try to set the timing to 4 degrees BTD it will barely run there. If I advance it a whole lot, like almost to the next plug wire, is where it runs best with and without the bypass wire hooked up. When I hook up the wire the timing does not change. It does advance when I rev it. It misses some at idle and runs weak like the timing is off. Some spots around 1/8 throttle seems OK with power. Giving it good throttle is a toss up. Sometimes it runs OK and most times it falls on it's really weak with a small misses. I have no codes showing. I was thinking it jumped time, but that wasn't it either. I don't think it is fuel related because it sprays good but doesn't want to idle at 4 BTDC.

I replaced, timing chain, ICM, cap, rotor, plugs, wires.. The distributor and firing order are set correctly and double checked no less that 5 times each.

I'm pretty much down to the ECM and or the lack of knock sensor and ESC. I did read that some ECMs didn't use knock or ESCs. Maybe the mapping for the box truck is just not compatable for my set up? Could the lack of back pressure from having headers and free flowing exhaust be the problem? I did install dual O2 sensors. Also I used the C1500 wiring harness because the box truck harness was to short to work, but I was told elsewhere that wouldn't be a problem. The harness I am using does has a spot for a ESC and knock sensor. The box truck harness didn't.

Thanks in advance.