Id be tracking down the issue first before throwing other items into the mix. Your running the same cams as I am and cubes did to start, which worked fine.
Not sure if we mentioned it, but Cubes looked around and picked our engine builder at the time we did ours. The builder was also the machinist, who was used to do v8s. No special knowledge of RB motors, only going off the information Cubes gave him. Its an almost proven setup, you just need to find that gremlin.
If you get stuck finding cams, ive got 2 sets here and cam gears I can lend you.