Hard Start only when engine is Hot

My 2000 Bonneville vin 3.8-K starts easily, at the first time, when engine is cold. But after engine is hot (200 degree-midline), it gets difficult to start (hard start), sometimes I have to push the gas pedal several times. Once it starts, it runs smoothly. Once gave me code PO034, so I changed spark plugs and wires but the problems still there. The code was erased and has not show-up again. No engine/service soon lights. Any idea?