Yeah its valve stem oil seals if its smoking on idle isnt it?
If fair amount of smoke at first start up, it is good indication of worn stem seals, cause oil weeps down em when stationary and pools in the pots, when fired up clouds of smoke which diminishes after a while to nothinh noticable depending on amount of oil, could take 5 - 10 minutes at least to clear, till next time it sits for a while. Once running, the oil is still getting into pots but is being burnt immediatly before it builds up enough to cause noticable smoke.
All the valves should have stem seals, dont know how far back the LR fella is talking, but 3.9 has em on all valves.
On the smoking like a bitch on idle, it will most likely be wear in liners and rings and valve guides allowing oil to be vacuumed in, as at idle you have greatest vacuum in pots,also happens at higher revs but then its more to do with blowby pressurising sump area forcing oils up into pots . After a while this oil will foul ya sparkplugs, have you checked them.
one other area to consider for rough running is hydraulic lifters, if they're shagged can cause problems, but you should hear them if they the cause.