I had the same trouble turns out my fuel pump was failing, it would do as yours was doing after an hour or so I live in the mountains so its hard on everything. drove me crazy trying to find the problem. I saw where testing symptoms they would let the engine run until trouble showed up. set up my test gear and after an hour twenty minutes the fuel pressure went wild from 47 to zero and back, never took it out of park, no trans,involved at all engine temps were all very cool less then a quarter tank of gas I was testing that the fuel pump was getting heated up and caused trouble, new engine two months old and was breaking in new trans when this started on my test drive, new sensor all around so fuel pump was all that was left that could give out trouble and never set a code was the fuel pump. I had all kinds of missing and cam crank codes that would show up though. I ve got the old carter out will take it apart an see for sure top of pump looks to have a crack in the plastic motor case but cant see real good anyway ill take it apart. and see. hope this helps.