Cranks/Starts good, feels like one or more cylinders gone. Cycling key (longer glow plug time) no change. No codes present. Replaced driver side glow plugs. No change. At normal operating temp. runs great, lots of power. Have factory manuels but not much info on driveability if no codes present. Problem only exsists when sitting for more than ~8hrs regaurdless of outside temp. Where should I test next, or is this a common issue? Thanks. Keith.