I also think it's a sticky/non-seated ring thing. Rislone used to be a good additive in the old days and you could google unsticking rings, but I think the advice you've been given, to drive the car, is good advice. It appears that it's already working with the rise in compression, so keep at 'er. Hopefully you didn't use a chrome ring in your rebuild, since they're extremely fussy to get seated. Good luck with it.