I have a 92 buick lesabre limited 3800 v-6 125000 miles. when i drive the car normally it runs ok when i accelerate fast it falls on its face then picks back up and when i come to a stop it stalls then starts back up. some times it accelerates all right most of the time it falls on its face when it does this some times you can slightly hear some noise that sounds like a back fire through the air box .some times at a idle in park if you rev up the engine then let up on the throttle it will die usually. sometimes just idleing it surges and dies but not very often. i have changed the catalyic converter checked the fuel pressure it is 40 psi at idle plugs are in good condition no trouble codes except for a code 58 .could the fuel pump be going out and still show good pressure at a idle ? would this not show a lean fuel mixture trouble code ? i have also checked the air filter. any info would be helpful thanks