GMC Repair: hesatation problem, mallory distributor, gmc jimmy

Question
I HAVE A 99 GMC JIMMY 4.3 VORTEC 90,000 .IT STARTED TO HESITATE AT ABOUT 20-30 MPH AND OVER 60 MPH. MY GAS MILEAGE DIPPED TO 10 MPG FROM 15. CHANGED THE FUEL FILTER , NO HELP CHECKED THE CAP AND ROTOR. THEY WERE NOT BAD BUT I CHANGED THEM ANYWAY AND THE PROBLEM WENT AWAY RIGHT AWAY. STARTED GETTING 17 MPG NO HESITATION. NOTHING . THEN AFTER ABOUT 1500 MILES PROBLEM IS STARTING TO CAME BACK. NOT ALL THE TIME BUT I CAN FEEL IT EVERY NOW AND AGAIN. JUST LIKE WHEN IT STARTED THE FIRST TIME .COULD IT BE A BAD DISTIBUTOR? ANY OTHER IDEAS?I PLAN ON CHANGING THE WIRE IN ABOUT A WEEK OR SO SINCE I AHVE A EXTRA SET.THE WIRE ON THE TRUCK LOOK OK BUT I WILL CHANGE THEM ANYWAY

Answer
I would check the wires with a tester or use a 3/8 bolt, check and re gap the plugs. Pull the distributor and check the roll pen in the gear. Personally I would change to a Mallory distributor. If you have the problem after all of this, email me:marvin.saunders69@yahoo.com