bubbling like that usually means headgaskets, and do be honest those symptomes sound like my legacy. Up to a certain mph it was alright (i sure it was overheating but the gauge is poopy) after that threshold it shot up too quick, just like you said. Pulling an engine isnt TOO hard, you might be able to do the hg's with the engine still in the car though. Depends on how much clearance there is. At anyrate, a hydrocarbon test would be best, and good luck.