2.2's usually leaked external(driver/pass rear corners)so a compression test won't show a thing!Look for green/white stains at block/head.Coolant level drops and you get air pockets causing your guage swings.The heads have been known to crack between the seats,but it causes no problems(similar to magnum heads)If it were mine I'd pop the head,clean the gaskets,install a 2.2 turbo head gasket and put it back together!Remove the plug in the head(above t-stat,sometimes a switch or sender)when filling to elimate air pockets behind t-stat.Hope this helps,I've done quite a few of these back in the day!Good luck!