I think those UNI filters have more constriction then my prefilter RAM AIR I made....and I have no issues whatsoever....I have played with fuel trim and run it currently at +15...but also ran it at 0 and was fine.
works awesome in powder snow too...the powder flies off the prefilter easily...however Ram Air is loud at speed,If you want quiet then you definitely need to go with stealth designs...anyone who has heard mine or rode my sled,is addicted to the sound...I love it!..LOL
Im not a big fan of the underhood box mods,or the unifilters...IMO RAM AIR will always make more HP at speeds...radar gun doesnt lie.
I agree with ALLEN here....those may be more constrictive.
Dan