Runs bad almost stalls

Last tune up as way b4 I owned the car lol about 50k ago I would say. No codes it is a spider system less then a year old. Ill have to check the fuel pressure tomorrow when I can get use of a gauge.

Checked the fuel pressure its holding at 57 to 60 PSI key on and arond 54 to 55 running it drops to around 40 to 45 when atempting to start the motor then right back up to 60ish when I stop cranking. So we checked spark in a few of the wires and some were weak but not enough to not start acording to one of my mechanics at my work. So next step was poping the intake to peak at the spider and there was some gas laying around and the guys told me that was the spider going bad so we put a new spider in and put it all back togother and it still would not fire so I checked the plugs they were fouled so bad so I put some new ones in and it started up fine and seamed to run fine till I went to leave work tonight I went out and started it took a second but started I rev it up a just to check and I felt that miss and spit and sputter again just slightly so I went less then a mile up the street to get gas and ran fine. Got my gas started fine rev'ed again and spit and sputtered again harder so I just took off got maybe a 100 yards and got worse stalled out and backfired once hard sounded like a gun going off lol never heard a car backfire that bad. So I pulled over and atempted to restart and nothing tried a few times and nothing so my friend was still at work she grabed a truck and pushed me back to work kinda funny as people watched that sight lol.