hard to start

i have a 1997 sts and it starts up rough and normally won't start on the 1st try most times will start on the 2nd have changed plugs and wires which didn't help it will also give a pop under the hood if the gas peddle is pressed when this is happing ..if anyone can help me ...THANKS..

i have a 1997 sts and it starts up rough and normally won't start on the 1st try most times will start on the 2nd have changed plugs and wires which didn't help it will also give a pop under the hood if the gas peddle is pressed when this is happing ..if anyone can help me ...THANKS..
I would check the fuel pressure regulator located under the top engine cover--also if the head gaskets are blown it will do the same thing--due to coolant leaking into cylinders--