many years ago we had a pro built 383 drag engine built for my sons camaro, 2nd trip to the track we seen the oil pressure drop just like yours, shut it off took it home pulled it apart everything was good, long story but it all had to do with our great FRAM oil filter, then i went online and read some really bad stuff needless to say i will never use them again, not even sure you use a fram, just a thought, good luck with your engine.