Bowtie
Gearhead
I dont know if there is an improvement in flow and hp with the aftermarket setups. I do have experience in the area that "certain" aftermarket filters do not filter as well as stock setups.. I argued with BSnelling about this until I gave up. If you are building a hotrod toy, it doesnt matter so much, but if its a work saw I would be wary. I really dont think the stock HD filter setup is that bad. Just my opinion.