How much oil are you using? How many miles since rebuild? There are a few things to check. Does is smoke on start up or deceleration? That would be valve guide seals. Does it have a extra bit of blow-by? That would be unseated rings. Disconnect the pcv and remove the oil cap to see if you have excessive blow-by. What heads and manifold are you running? Could be a leaky intake manifold gasket but that would usually show up on one or two plugs. When you say the plugs look great I would bet on valve guide seals but it really depends on just how much oil you are using.
SimS
