I had a very simular problem, and these two guys who keep offering help are the reason my problem is resolved. I also had very low vacuum, and I also smoke tested my system, and I did find a few problems. But, there were other vacuum leaks: 1. The vapor canister valve leaked vacuum. 2. The TAB/TAD valves both leaked vacuum. None of that showed up in the smoke test. But now I have a good 16-17” and it runs great.
I also kept searching for an unknown problem, instead of dealing with the low vacuum. But once I stop searching for another problem, I was able to fix it. And, you have a cam that you don’t know the effects it’s having on the engine. I just would try and completely eliminate any vacuum problems, because we know these setups are very prone to them.
I’m sure the solution is just around the corner.