spark knock

i have a 98 ss pretty much stock. it has a spark knock at around 3500-4500 rpms with 93 octane fuel, why?

Ported MAF? SLP timing tricker? HPP tuner? These can all cause spark lnock.

But it's probably carboned up piston heads. Seafoam it.

Could also be PCV issues. Check your intake for oil...