1989 Isuzu Amigo 2wd

I'm stumped. I bought this Amigo a month ago. 2 mechanic shops later, no one can seem to tell me why it gives trouble starting cold. Once you get it started, it runs really well. (except for the fact that it revs up and down on its own at times, but not consistently) 4 mechanics are completely stumped as to the problem. They started out telling me it was a fuel problem no most think it's an electrical problem. We've changed fuel pump, regulator, filter and plugs. Check engine light is on also. Any ideas? I'm about ready to push it off a cliff.