PO442 code, what to look for

My '98 Bonneville recently lost a fuel pump and regulator. Upon replacement it runs fine but it threw a PO442 Emmissions, Evaporator something or other (small leak). Any idea what or where to look for this? It ran bad when we got it back and we had the code reset. After a bottle of fuel injector cleaner it runs great but the code came back. I reset it tonight and we'll see if it reappears.

There is a small leak detected in the EVAP system, did you replace the big O-ring seal along with the new fuel pump?