97silvermaro

couple weeks ago water got in the opti from a leaking coolant hose. there was a backfire the car stumbled 2-3miles died. replaced the opti (brand new ac delco) car fired right up. car will crank and idle fine but if i try to pull off the car surges like its not getting fuel. its worse some days and better the others. the pump has only 1000 miles on it (walbro 255lph with the racetronix harness) and if i take the vacuum line off the fuel regulator pressure is 43-44psi. when idling and i open throttle pressure goes down to 32-36psi (vacuum line attached).
is there a sensor i should check that may have messed up when the opti fried? thanks guys for your help