Bad Idle at start up 5.7 tbi

This thing is driving me crazy! When I first start my 87 5.7 tbi pickup in the morning or after sitting all day at work it idles up and down for about 30-45 seconds. When it drops it sounds like it misses then perks right back up. It sometimes has a rough idle after running for a while and seems to have poor performance when cruising. But other times is just fine would never even know there was a problem. I have checked it with with my buddy's scanner and nothing seems out of place, no codes. Has new plugs,wires, rotor, cap, pcv valve, map sensor, fuel filter, and air filter. And what makes it worse is when anybody else is around it runs like a champ, go figure. Before I turn grey trying to figure this one out does anyone out ther have any suggestions?? Thanks, for any help anyone might have.