Thanks Rockland Valley!!There is something off big time 100 psi on a Briggs is bad, and 50 psi difference is bad as well. You have a issue with that one cylinder, likely a valve/push rod issue as those are common but so are Briggs head gaskets. We have videos on Briggs head gaskets, valve adjustments and bad head gaskets and many other things. I would pull the valve cover on the bad side its 2 nuts and may give you a answer in 30 seconds. https://www.youtube.com/@caseingersolltractorsnortheast/videos and welcome from Case Ingeroll Tractors Northeast!
The repair shop that I took it to today suggested that could be a possibility too!
Thanks much for the feedback!