need help with my vortec 350. wont start unless peddle is half way down.

so one day i went to start the van and it didnt wanna start. sounded to me like it wasnt getting gas. so i put a new fuel filter in it and ran a seafoam through the tank. still ran like crap. so then i changed the fuel pressure regulator. still no go, then removed the spyder injection and put that in still. no. checked fuel pressre it was right about 60.even when we turned it off. so dont think its fuel related. then thought maybe it was a spark issue. so i changed the cap rotor and plugs. and its still not starting w/o the help of the gas peddle. no codes are popping up either. anyone have any ideas or had this problem before. please help.

by the way its a 200 chevy converion van. fuel injected.

Might have a clogged cat

fuel pump might be weak, my truck did that the other day and only way i could crank it is if i chocked the throttle body by hand or pour gas down it and it would run like a champ, mines a 96 vortec