you arent using chrome moly rings are you? ive had alot of bad experiences with those not seating properly do to the hardness of the material. i like cast rings better. with all the ring work you did....did you make sure the ring gaps werent lined up? i dare say that unless you have some bad valve seals its gonna be your rings. if you take the head off..pour some gas in the valves and make damn sure they are seated properly. and look at the rings in #4 and see what the problems are there...check for some taper wear.