I have an issue with my 98 1500 6.5 "s" . I have the p1191 which is intake air duct leak code. At first it happened once a month or little longer; as time went on it steadily got worse. I check the usual things first intake manifold gasket, riser gasket, all the clamps, checked for cracks in the hoses. Found nothing. Changed mass air flow sensor with a used but good one. While replacing the maf found part of the plastic next to the maf was cracked, so patched and repaired the crack. NO code for about three weeks, then came back. Replaced map sensor since the two work together. Helped for about a week or less. I have a code reader that gives freeze frame data, so I have been keeping track. 95 % of the time the code sets at roughly 35 mph and the same mass air flow %. I have got to the point where I have been checking it with the code reader every time I drive it long enough to let it warm up to operating temp. Sometimes it will go one trip sometimes two or three before it sets a code. I have checked the rubber hose and clamps again plus everything else I could think of including the ground at the back of the engine. What am I missing? This is driving me crazy try to figure this thing out.