Torco is real octane booster, not that cheap crap you buy at the parts store. This stuff really does raise octane rating by the amount given.
Octane rating and knock do not go hand and hand like that. Getting 5º of knock on 91 doesn't mean you'd see 3º with 93 octane.
Do some math and run around 98-100 octane and see what happens. I think you'll have to up your pulley size in the end because 6º of knock on a 3.0 pulley is alot. It's more dangerous than 6º on a 3.4 because of the added boost pressure.
