Hello, ever since the weather degrees has dropped i have had a problem with my 1978 Chevrolet Silverado 1500 with a 400 6.6l truck. I would start her up and let er get warm for about 5 minutes. At this time the heat guage has moved a little. I then get about 2 miles down the road and when i go either a constant speed or varying speed the truck will soon almost skip a beat or trow your body forward with a blurp. After the guage is fully up and the truck is warm it will only do it everynow and then. I adjusted the automatic choke and richened the carb out. I even went to a junkyard a got a thermovac air cleaner with duct and fleiable tubing going to the header. After all the work it still does it. Can someone please help me!?!