Your issues sound almost identical to mine. I spent nearly 2 months diagnosing it and it ended up being the BPV. Here's my thread if you want to compare datalogs and such:
https://www.ft86club.com/forums/showthread.php?t=137808
The TL;DR is that it was a combination of an absolutely garbage tune from Edelbrock as well as a faulty BPV which didn't seem faulty under multiple smoke/pressure tests.