I have the Hypermax cowl inlet on my truck, when it was NA with 3 1/2 exhaust with a race bullet muffler and home made Y pipe. With the factory round filter housing and a K-N filter in it. The truck had a better responce than when it was stock ! Now turboed with the Banks sidewinder cone shaped K-N air filter in that plastic housing from Banks hooked up to the Hypermax cowl inlet, it worked OK, but was much more responsive with just the open filter ! Next I put on a 5 inch
cowl hood with the back opened to the windshield on it, and left the Hypermax cowl inlet on it wide open, so I get real fresh air under hood. That runs really great now ! But not to leave well enough alone when I staight piped it (just removed bullet muffler) and piped in my RDT where the muffler was. No more smoke in the cab, sounds bad a$$ with whistle and exhaust, tows great,good power and I am very happy with my truck after having it since new in 93. It should be painted this spring , got alluminum dually rims to go on when I get tires.
Mike