i did my valave covers about 6-7 years ago, had a bad fuel-rail gasket on the intake and the drivers side cover was leaking at that time, in the last year ive noticed my driver side cover has started leaking again, i remember back when i did that job the cover had kind of a bad spot at the bottom edge near the firewall end. gasket used were (i think) a fel-pro brand, all i really remember was that they had metal rings where the bolts went through to keep from crushing the gasket when you tourqued the bolts down. intresting thought on the pcv valve...min is original, truck has 160K+ miles on it, havent treid tightning bolts, really only notice the leak when i shut off the truck and i see the oil "smoke" creeping out from the joint between the hood/left fender. too damn cold right now to do much outside. (unless its a emergency)