Yeah I understand that, just lookin' for numbers. The factory one is just a hair more restrictive and less efficient with the paper filter, accordion tube, and silencer box, but nothing that's seat-of-your-pants noticeable. I did a lot of research (as I do with most things I haven't tried), and almost bought a new one before finding this one, but I can't seem to find anyone besides Volant themselves who has any solid proof of gain. Plenty of people swear by it, but noone has any actual proof of increase, be it in HP or MPG. I'm not stressing over it, just curious. It's really more for underhood show than anything. I'm putting the truck on the dyno when I get the swap done anyways. Nothing special, it's an 80,000 mile (very clean) engine and the only major things I'm doing is a full gasket set, 502 Marine cam, LS1 injectors, mid-length headers, steel rollertip rockers (lame, I know, but every point of resistance counts), and 411 swap. Also doing small simple stuff like porting the throttle body, MAF, and intake, running thicker plug wires, using a low resistance coil, and dual 2.5" exhaust with high-flow cats and crossover muffler (works kind of like an X pipe I guess, probably not as efficient, but it's what I've got. Also toying with the idea of electric cutouts, because, well, why not?). Most of which I have already done with the smallblock and has worked out pretty well. I'm not trying to make crazy power out of this truck, it's my daily, I'd be happy to see 320-350HP at the most. Besides, I've got another beast under construction to play with haha. And I'm using my spare L29 harness to inject it!