What are those knockout plugs made of?
I recently changed out my wife's hockey puck in her air intake and the puck had a different diameter where the clamp was versus the bottom that was in the air stream. She had been getting some oil pulling through the PCV into the throttle body but we corrected that. I guess that the hockey pucks don't react well to petrochemicals. :P
We were chasing idle issues on her car only to find out that the clamp around the puck kept loosening up. That's where we found that the puck diameter had changed.
1968 Camaro -my first car.
1995 Purple Pearl B4U Caprice
1995 Black/White 9C1 Caprice--NADACOP
1995 Purple Pearl L99 Caprice
2012 Alto Gray Metallic 9C1 Caprice--The HoDag-Solo axle back exhaust, improved racing OTR CAI intake.