Dom, when I dynoed the 434 the guys at the shop asked me what air filter/air cleaner I ran. I run a K&N 3" filter with the filter top, The dyno operator pointed to an AllStar top and base and told me that is what I need to run along with a Wix Racing 4" filter. He said for some reason the filter top really messes with the afrs on a 4150 Holley, not so much on a dominator. Think I'll order one just see.