engime miss and CEL 88 f150

ok... its not running fine... after removing the plenum to change the valve cover gaskets on my 88 f150 302.... i now have a miss and a check engine light it showed up immediately after... it sounds and feels like a vacum leak.. but ive gone back over it 4 times and found nothing... my ford tech buddy looked at it real quick and found nothing.... he didnt have time to really dig deep or run a check on the CEL... when you spray carb cleaner all around there is no change .. i thought i might have gotten something under the plenum but sprayin under and all around the plenum there is no change.. you do get some change when you spray the EGR valve i removed it cleaned it still the same... it has about a second hesitation from idle to acceleration... also it smells kinda rich... ive noticed kind of a whirring sound under the hood while accelerating that i cant remember before ... (its a 5-speed) i know its hard to diagnose over the internet but maybe some of you have had the same thing... i always seem to come up with the weird stuff.... please help