My point is the main power feed wire from the battery...first place I would look. Also the ground wire is a good point as well. You should trace the main feed to the starter, fuse box, interior fuse box, ignition...this main feed is a hot one, but a ground wire will cause the same symptoms... I just had a wire to the fuse box on the Tahoe cause starting problems. While looking for that connection, I found other connections corroded. Side post terminals were really bad after I took the plastic covers off to inspect, as well as starter terminals...cleaned them all, but the fuse box connection was the problem. Probably started back when I wired in the electric brakes for the car trailer...anyway, certainly sounds electrical, and James may have a good point as well...seems the RCM can cause a lot of problems. Rudy would have the best test equipment for testing voltage...put the meter on, and start wiggling wires...look for a bad connection...good luck...