blazer problems plz help

i have a 97 blazer i took it out to the mud but didnt go threw all that much a lil bit of water not alot, it is sputtering and running shitty when im going slow and slowly pushing the gas it will accelerate fine but if i push down on the gas hard rpms will drop and it will not accel

replaced the wires and plugs
put sea foam and injector cleaner in it
and replaced the fuel filter

if im in neutral and i put the gas to the floor it will make a popin noise and rpms will drop

took it to the auto parts store dianostic test said it passed

any idea what this could be

Did you check the cap...could have got water under it....I went threw a shallow puddle once and somehow got into the cap....ran fine after I dried it out....just my 2 :2cents: