My 18hp craftsman lt 1000 sputters and stalls as soon as I go up a slight incline. Checked the easy stuff, new fuel filter, air filter, plug still does it. Any ideas?

The first thing I would try is to take the gas cap off and see if that makes any difference. If the vent hole is clogged it will make it act like it is running out of gas because it can't circulate the gas and air. Or, if it has the gas tank in the rear of the mower it will have a fuel pump on it. It could be getting weak and need replacing.

If neither of these things make a difference reply with the model number from under the seat so we will have more info to work wit.