I am thinking this truck is running lpg if thats the case on the top of the lpg assian converter you will see a chrome plug sticking up the top is sealed break the top plug out in side is a screw turn the screw about 1 turn to see if it fixes it that is the air fuel mixture. Try in then out until the surge is not there. If that does not help you could need to clean the butterfly plate under the air horn take it out but be careful try not to get any cleaner near the moter of the govern or tps switches. Good luck