Hey guys,

Is there any data out there (like dyno numbers) how well the stock SU air filter box is working compared to 2 round K&N filters? 

I installed a K&N filter mat (for the stock air box) and did not buy round filters so far. Top end engine performance is not great, it feels like from 5000 rpm on no further power is gained. A/F ratio is spot on, though (wideband installed). Of course this could also be due to the relatively small SUs on a 3.1L stroker.. I just love the simplicity of SUs. And much more budget friendly of course :) 

BR 

Here's some good reading on the question.  https://www.google.com/search?rlz=1C1BOFA_enUS494US494&ei=n3NUXLboM6ip_Qax0qWoBQ&q=stock+SU+air+filter+box+is+working+compared+to+2+round+K%26N+filters+classiczcars.com&oq=stock+SU+air+filter+box+is+working+compared+to+2+round+K%26N+filters+classiczcars.com&gs_l=psy-ab.3...1209.6599..7093...0.0..0.101.1250.16j1......0....1..gws-wiz.......0i71.2D2caPPCrBo