i blew a freezeplug while driving a few weeks ago, the truck overheated and started knocking some before i get pull over at a safe spot. i replaced the freeze plugs and had no more leaks from them at all, not even a drip. so 3 or 4 days ago the truck started running rough, and smoking white upon start up for a few minutes. no chocolate milk oil that i could tell. sound like a headgasket? anyone have any further diagnostics that i can try???