I think that a clogged pcv system would cause the engine to run rough but not to smoke. As far as plugs, the guys here, at least for the gen 1, recommend ngk. I, due to the length of the job would certainly install a platinum of some sort. Anyone here have input on iridium plugs?

Active duty US Coast Guard helicopter mechanic (IA)
87 Monty
2.6
auto in progress
31X10.50 mudders
ARB
Warn 6000
Many hours of sweat and pain
Previously Badas87-2dr