DRD

My 1995 F150 with a 5.8L with 48,000 miles has recently been starting to run rough and not wanting to idle very well for several seconds after the motor is warmed up. This happens after you turn it off and go to restart it about 10 minutes later. If you push the throttle it runs fine after that. I have checked the codes and have no codes. I have also replaced the spark plugs and fuel filter. I was wondering if this might be a problem with fuel vapors getting hot after setting there or a problems with the injectors. What do you guys think? Also, after purchasing this truck about a year ago I have always been wondering how the 5.8L should idle. Mine seems to be a bit rough and have a slight vibration but when you put a small load on it, it smooths out. Is this pretty normal for this motor? Thanks in advance.