If I understand the filter arrangement they're facing forward so that at high speed the drag actually causes a bit of a vacuum around the base of the filter and that might actually reduce the intake volume. Personally, I'd pull a spark plug and look at the tip and see what kind of mixture you're really burning. And, if he put a bolt into the AI tube how is it really sealed ? Enough air to booger the intake mix could still seep in past the threads...
