Re: Cub Cadet 1440 stalls out
Coils are a good place to start, see if the new ones make a difference. I'd change out one at a time to isolate which one is bad, then install the other new one and keep the good old one for a spare, assuming this fixes the problem.
See if your gas cap is venting properly. Either run with the cap loose to see if the problem goes away, or wait for it to stumble then loosen the cap to see if you hear suction and the tractor rpms pick up again. The 20 minutes is ususally the right interval for gas cap problems.
Finally, put 2 new spark plugs in if you haven't already. The stumble and difficulty running the pto probably means one cylinder is firing, the other not, so an intermittant plug insulator break or plug wire could be the problem. I doubt it is a carb issue, you start and run fine, then re-start fine so it sounds to me like the carb is OK. Good luck!
CC 1864, CC 2084, CC 3204