Power wash your engine. If there are any intake or vacuum leaks, they should show up now. Use GUNK orange at a DIY car wash. Make sure that your throttle body, plate and idle air control valve are showroom new with no sludge of carbon build-up. Remove the throttle body to clean, if you have to. Amzoil Foaming Cleaner does a great job. Are you sure that your valves are adjusted properly??? Check your PCV valve and hose for signs of collapsing or deterioration. Good Luck!!