Funny you are seeing that on a 4.3. I fixed an Astro van once upon a time with a knocking HO 4.3 TBI. The fix involved first seafoaming the truck. That halved the number of knock counts I was seeing. Then I checked the fuel pressure because the BLM was running over 135 across the board. It was at 9 PSI. I broke the factory spot weld and increased the pressure up to a more desireable 12 psi. Finally I dropped the PE settings to a more appropriate throttle position. High Load + Closed loop = Knock
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