i did a motor swap from 4.9 88 model to a 91 model 351w. the 351 come out of a e250 van. when i was doing the swap i got the vans computer which was the automatic 4 speed. i put this all into my truck which is a 5 speed manual. ok here is the question i took the wiring harness off the van it was to short and got one off a 93 and put on the motor. it was a different harness. got a plug in for each injector and just one main one at the back. the one off the van had way more than this. now the truck runs but not well at low rpms should i swap the computer from the 93 in to my truck as well. thanks for the help ahead of time .

 

Not an expert but two things spring to mind. You probably should have the transmission Range Sensor plugged into the harness as the computer will be "looking" for a trans. Also, unless you have already changed it, the fuel pressure would be too high with the original fuel pressure regulator.
Hopefully some of the experts will give an opinion.

 

You need a computer for a 5.8 and either a C6 auto or manual transmission, and you also need a complete engine harness(all of it from the engine to the computer) for the same combo. Anything less will not work right.

 

the fpr comes on the back of the motor it is the one for the 351w i just checked the fuel pressure sunday evening it is 36 key on eng off 31-32 eng on. 45 without the vac on it so that is good low but with in specs of the books and what i have found on here. and i was thinking i need the other computer also guys thanks for the help with this