power valve makes my 440 ping??

ok so I swapped back to the power valve blank and it pings less but its still pinging. I tryed spraying carb cleaner around the base plate and intake, nothing happened.
anyone got any ideas? change the fuel? I filled it with 98 2 days before the pinging started.
ill change the base plate gasket and have a look in the plenum, but im running out of ideas :angry7: any help would be great, thanks Tim