Computer Problems B2200 PU

I have a 1992 Madza B2200 Extended Cab 5 speed standard pu. I am having computer problems which I believe could be fuel related. The original computer starts the truck without a hitch, however it runs really bad...Bought a good used computer but it wont' start the truck. I have to start the truck with the original computer, let it run for a few minutes then switch to the used computer. The truck runs great with the used computer it just won't start it.....

any ideas on what the prob could be.....really need your help...

Is the truck Carbureted or Fuel Injected? I'm assuming its FI as if it was carbureted it should still start with a bad computer.