I doubt there's any noticeable performance difference. That said, JLT's 123mm/127mm intakes originally came with 5"x9"
S&B Powerstack Air Filters.
There were a couple of lengthy threads about suitable filter replacements leading up to a
Group Buy for AIRAID (#703-496) dry blue "Synthamax" replacements I ran several years ago. For reasons that escape me, they discontinued the blue version but (last I knew) still make the red version (formerly #700-496; now, apparently,
#701-496). At the time, they could and would still produce blue versions @ $120/ea for orders of less than 10 units and $95/ea for 10 or more. Good luck!