To confirm the above comments on the effect of the little Stelling and Hellings air cleaners, I ran two back-to-back chassis dyno runs with and without the standard 1 3/4" x 9" paper elements and with the air cleaner bases on the carbs. I got 397.47 HP/431.92 LB-FT with the filters and 406.15 HP/441.19 LB-FT with the filters off the motor. No difference below 3200 rpm, then a consistent difference above that all the way to 6000 rpm...maybe that was where the secondaries opened?
Like ItBites said above, the 7.82 HP/8.34 LB-FT increases works out to 2.18
1.98% increases...it all adds up, but that's not enough for me to notice or make it worth running without filters...
Now the cold air induction angle...I like that part, but the scoop? IMHO it's more for style than function.