1991 Pontiac Firebird Fuel Issues

I have a 91 Firebird and it has 2 problems when I start the car it will run for about 5 minutes then die then after a couple of minutes and keying the ignition it will start again run for a little while and die again and it's just a continuous cycle it has new plugs, new computer, and. Well many new parts minus the fuel pump, fuel filter and plug wires. The second part of the problem is after starting the car it smells VERY heavily of gas and I can lose an 1/8 of a tank in five minutes, so I figure gas leak but the confusing thing is I parked it on a dry concrete slab ran the car and revved it up a little bit and there were no fluids on the ground but still smelled heavily of gas and the gas gage did go down quite quickly. Please help, i'm confused.