What kind of vehicle is this motor in? I have a 77 4 bolt with the same top end that I put in a 93 pickup that had a v6 in it. Needless to say that chip had to go. It took a lot of research to get the right one. You'll need the best parts guy at the local dealership if you go that route.

I also have a problem with inconsistance idle too. Out of the clear blue the motor will idle up to about 1200RPM. This is a idle control related problem and I think I have it narrowed down to the connector. The wire is just worn out and not making a good connection.

I have the RV cam that Crane makes in it, I didn't want to go to big on the cam because I was afraid the computer would be fighting to compensate for it. You may want to talk to the technical folks at the cam manufacturer.