Weird. I heard what I think is audible knock when I nail the throttle and the boost kicks in. Then it goes away once I get moving. The SM shows nothing except for 1-3 degrees on the shifts. Anyone else notice this or have experienced this? Boost is only set for 14-15 PSI. Chip is new 50# Extender with 23/21 timing. It's also on CA crap gas. 91 octane.... It also may be time to change out the old fuel filter.... But why knock only when I floor it?