Super six set up with low comp

Always suspect data. Your 90 psig data doesn't jive with "idles and runs great". If it doesn't burn oil, I certainly question 90 psig. Turn the motor over by hand. If you must fight each cylinder (3/rev), your engine is fine and your compression method is suspect. You need to remove each spark plug tube and use a screw-in gage w/ an O-ring seal. The Shraeder valve in the tip of the gage must be correct and not binding (opens real easy). Gage must be accurate. If a shop that will do the work collected the data, suspect "data bias", i.e. they might have rounded off a 143 psi reading to say 90 psi, or perhaps they have a gage that always reads 50% low, but they like it because it makes a lot of money for them, as they say with a straight face, "the readings were ...".