[s-cars] Knock knock knock with MTM & CA 91 octane fuel

[Rob Pecsar]

Installed my MTM upgrade yesterday here in sunny California, land o' 91
octane.

At partial throttle I do notice more torque and possibly that the boost
gauge comes up quicker. However, quickly stepping on it to more than ~
half throttle gives me unquestionable pinging (knocking). Don't want to
push it to WOT until I resolve the knocking.

Any suggestions or BTDT:

Using premium (?) Chevron
Going to check plugs
Going to check for Fault codes
Going to change Fuel filter
My Buick GNX friend is saying their group adds Xylene to there gas
tank...hope I don't have to go this direction.

TIA,

Rob Pecsar
92 S4 was TAP, now MTM with K&N, Samco, and untouched wastegate