I used my 77' 305/350TH/Np205 Jimmy to haul back a parts truck for a friend yesterday. Truck pulled great, except for the following puzzling issue: 3 seperate times after I filled up with gas, I would head back out on the road and this problem would occur. I would start to climb a long grade on the Interstate and half way up the motor would start to miss. No drop in the gauges, no dim in the lights and as soon as I let off the gas the motor ran smooth. I would pull over, let it idle and then take the rpms' up to about 3K...no problem..off and driving again. Drove the Jimmy to work today, without out the trailer and it ran great, even up a grade!? Only failure I had was the pass side exhaust pipe came loose right by the down pipe, but not unattached. Any ideas?