2000 explorer xls-P0455 leak not found

have 2000 explorer xls, 4.0, V6, SOHC, with 75,000 miles. check engine error code P0455, large emissions leak, triggered. diagnostic smoke leak detector used, no hose leaks found. had locking gas cap but original fuel filler cap was replaced for leak test.
vapor canister purge valve behind left front bumper replaced.
other than replacing fuel vapor storage canister, vapor canister vent, could the fuel tank pressure sensor or fuel level input device need
replacing as well. thanks
naeem
Did you try the test with your locking gas cap? You said you did the test with original cap. If you did not test with locking cap, there is a possibility the cap could be leaking.

Being way2old is why I need help from younger minds thanks way2old.
both gas caps were used for tests. no leak found.
mechanic cleared error. check engine reappeared
within minutes. gonna try replacing storage canister, canister vent, etc., then fuel tank pressure sensor. really hopin' its somethin' simple.
thanks again.