idle question

[mrsmothers]

Well I went out and messed with the truck a little bit today its back fireing more and more I sprayed wd40 around the base of the carb and it didnt help. The gas is running a little low could it be that I have water in my tank and its sucking it up? The reasion why i ask is because when I first got the truck running it ran on its own for 20 min with no problems not it wont stay running inless I have my foot on the gas and when it gets in higher rpms the backfireing starts. By higher I mean around 1500 to 2000 rpm this is driving me nuts and with out another pair of hands on it its very hard to get under the hood with it running.