I almost forgot about valve springs. Non-HO and HO stockers will float with exhaust backpressure, even with 7psi on a stock engine.
For my buildup, neither stocker would work with the cams (coil bind). So, I used Crane springs for a modular Ford. IIRC ~95# seat pressure. Those floated too with backpressure on the exhaust side. Then tried a Competition Cams valve spring with ~135# seat pressure. Did the trick. And yes, it as exhaust valve float, not intake valve float (no change in AFR during power dip).
Run 10--stock engine, 60-1 turbo (7psi), stock valve springs (70-80# seat pressure).
Runs 6 & 67--built engine, similar boost levels (~7psi) before and after fix.
Runs 26 & 77--built engine, similar boost levels (~10psi) before and after fix.
Couple of notes about the dyno. Inertia type, system wouldn't boost as early as it does on the street. The power band on the street starts around 3900rpm compared to around 4300 on the dyno chart. Also note how choked the 4.7 manifold is after 5800.