I've seen a few people with headers, ported blower, open cone intake, 104s, 180* tstat and in car tune still get knock on a 3.4 pulley.
ZZP was saying they thought they found the reason behind this, they started to notice something as they would tear these engines apart, as you know the cylinder openings on the head gaskets are not perfectly round, and on some cars part of the gasket would hang into the combustion chamber, and it would get red hot and cause pre ignition of fuel causing the engine to have knock retard.