Hello, I have a Craftsman YTS4000 with a 24HP Briggs and Stratton engine. Had it for 2 yrs. I have been having an issue in which the mower will tend to stall on hills... not good as my entire 2 acres of mowable yard is a hill. It will start up fine and run for 1/2 hr or so, but then lose power when going up hill and eventually stall. Sitting for a while will allow it to start, but eventually die again. Ive changed oil, filter, fuel filter, plugs, air filter, cleaned carb... no change. Thought it was bad gas, drained tank and carb+ lines... new gas with stabilizer.... same result. I can order a new fuel pump, but thats not gonna get my lawn mowed today. Any other thoughts, suggestions?