It is your valve seals in your heads. They go bad after 15 to 18 years. lol Plus if you let your motor sit around for awhile before starting it up the valve seals will wither up and crack and get hard. Same thing happened to a client of mine. He finally got his motor started after a 2 year build you know saving up money and what not to buy parts and started blowing white smoke on idle. We checked the turbos head gaskets every thing and still couldn't find out why he was blowing white smoke until I told him that his valve seals were bad. We changed out his valve seals and walaa! Stop smoking. Hope this helps.
