I am getting a intermittent clunking sound from the fuel filter (or somthing with fuel system in that area). The clunking starts after the car has been driven for a while and seems to be worse when the engine/outside air temp it hotter. The sound started after I installed my (used) walbro fuel pump. I figured it was a problem with the pump because it went away after I reinstalled my stock pump. The sound came back after installing the second (brand new) fuel pump.

Current setup
99 Si
Greddy turbo
walbro 255 fp
B&M command flow
B&M fuel press gauge

The problem does not seem to be effecting the performance of my car. I would like to hear any suggestions before I start taking things appart.