1995 Chevrolet Suburban Transmission

1995 Chevrolet Suburban: 163,000 miles, V8 5.7 litre, new engine 15,000 miles ago, new transmission 20,000 miles ago, excellent condition. Engine had to be replaced because one of the long breather bolts broke and slid into the carbeuretor throat holding it wide open - way into red line rpm - shut down engine and coasted into an off road -damage was done! Since the new engine was put in (new transmission prior) virtually at all speeds and rpm’s the rpm's will momentarily jump up proportionately to speed. Most noticeable on interstate at 60-75 mph 2100 rpm's to 2300 rpm’s engine will surge 1000 rpm's to 3100 rpm's to 3300 rpm's. This is momentary but can be felt and heard then returning to normal. This may occur once an hour or every 10 minutes. The engine folks nor the transmission folks can figure it out?