HPOP Pump With and without valve? *15 or *17?

[Lunatic250]

I recently swapped out my hpop because i was told it was making noise. it wasnt the hpop and i put a hpop that a friend gave me which was a new reman. the hpop were i dentical the only diffrence was that the one i put on seem to have like a check valve in the front face and and the original one on the 1999 truck didnt. can anyone tell me if this is going to effect the performance of my truck at all? or what that valve might be?