its either a tuning issue or an air leak. Do you have the needles set at a good start setting like 3 1/2 out on the high and 4 out on the low? How hot is hot, what kind of temps are you talking about? a good way to find an air leak, is to put some nitro fuel in a spray bottle and spraying the engine and see if the idle changes, if it does then spray in that specific area and see if its still changing idle. also make aure the exhuast manifold is tight and that the exhaust manifold gasket is in tact.

also chack for a clogged fuel line, fuel tank or carb.