[buzzinhalfdozen]

I've personally made many passes with BP breakin oil in my engine, never had an issue with mine or the several engines I've freshened for other racers. Not sure that theory holds water, however the timing advice sounds like a likely cause. Hope you find it. BTW on the engines I've done for other folks , with a wet sump and vacuum pump I "request" they not pull more than 10 inches. That number is NOT a result of much R&D merely going off the condition of engines at tear down with a known amount of vacuum.