1999 4 cylinder 4 Runner... With 239K on the original motor.. Well I just put a new exhaust manifold on it.. and its runs better.. had a mechanic check the compression and it was bad.. #1 cyl..90 #2 cyl 90, #3 cyl 100 and #4 cyl 175.. Now.. He is telling me that they should all be at 175, and that doing a valve job will only make it worse. It has never had a valve job with 239K on it.. I am willing to take a chance. He said that the engine will "fall apart".. So my question is.. should I do that valve job or just drop in a rebuilt engine??