i rebuilt it and ran it around town its got around 100 miles on it and its just wicked doggy, i had cel codes and got them taken care of but code 51 comes on when i hit the gas, i have set it with all the specs and i did check it with the multimeter it is in spec, the timing it dead on, i have changed vafm. could it be an ect sensor? iv been pulling hair out over this for a month, it feels like it cuts out and it wont rev past 3500 plug colors look a tad rich but are new all the wires are too

 

Did you ever get this figured out? I've been battling my 2wd with the same problem. Seems like it is set to spec and I can set the timing just fine but when I have the jumper plugged in and hit the gas the CEL comes on with a code 51.