1995 gmc k1500

My 1995 gmc 1500, 350 tbi 5.7 v8 runs perfect. But
when i first start it, even when its warmed up,
sounds like its trying to flood itself. When i first start
it, i have to push the gas all the way to the floor and
then let off when she fires up, but for the first 30
seconds, if i give it too much gas, it trys to stall, if i
barely give it gas, its runs fine. After that 30
seconds, she runs like a top, any ideas why its
doing this?