Ford EFI 5.0 wiring in Ranger

[Andrew]

Hello everyone,
I am relatively new to the list but I have been playing with Ford EFI for a
long time now and own a 5.0 shop here in Canada.  My latest project has
been a 5.0 swap into a 92 Ranger.  I rewired the Mustang harness to fit the
Ranger and fired it up for the first time last night.  I can't say I am
very happy with the results.
Once it starts, the motor runs really rough; a heavy surge begins and the
car will eventually stall without throttle.  I know there could be LOTS of
things to cause it, but I would like a logical approach to find the
problem.  I don't have a break-out box but if it would save me some time I
would get one.

Any suggestions would be greatly appreciated.

Andrew