What can cause my 06 5. 9 to start to "clatter" and seem to miss at an idle it sounds like it's cutting out if you touch the fuel it stops. It has 125,000 on it, and runs like great. truck is stock with a K&N and straight pipe. It just started this a few days ago. When it's not doing this is sounds fine. I just don't want to mess up something that might be simple??? Any thoughts?