[teckenroth]

Thanks, I'll try the leak-check that you describe. The fuel filter was changed late last year. Ran injector cleaner through system late last year as well. I did replace one of the vacuum lines (5/8") that connects to the rear of the intake and a vacuum component located near the firewall, driver side. It was very, very soft (almost gummy). Will also check other vacuum lines as suggested.
I have noticed that the condition seems to be present during warmer months. Didn't really occur during winter months (in St.Louis, avg winter temp 45 deg)
Thanks and I'll post my findings!!