Here's my review of the V&H VO2 on a Street:
I love love love it, other than it being butt-ugly, but you'll see at the bottom of the thread that I think I solved that problem rather nicely. Now I not only love it, I frickin' love it.
I have nothing against the K&N; I've never used it, so I'm not knocking it, just reporting on my experience with the V&H.
One thing I never noticed, but now really do, is how sleek the VO2 is. The stock airbox looks like a tumor on the side of the engine to me now, as compared to the VO2.
K&N posted a chart showing
up to about a 6.7hp gain from using just their AirCharger - no exhaust change, no retune. Not only that, but they also posted a 6.1 ft/lb torque gain. That's a pretty big boost from just an intake change, but after experiencing the VO2, I think it's reasonable. With just the intake change alone, that makes up all the torque difference and half the horsepower difference that the new Street Rod offers.
As far as choosing between these two intake kits -- I don't see how there's going to be a performance difference between them; either one solves the main problem which is that the stock airbox has a tiny little hole it lets air into. Both the VO2 and the K&N have large-diameter pipes that are as big as the Street can accept, so -- there's really not any way to get more air in, without going to a forced-induction kit like a supercharger or turbo. If there's any performance difference it'd have to be from a freer-flowing air filter element, but both companies know how to make free-flowing air filter elements so I doubt there's any significant difference.
In the end, I decided on the VO2 over the K&N for a few reasons:
1) I didn't like the big, obvious, glaring look of the K&N; even though it does look exactly like the Lowrider S, I just didn't like it. I hated the look of the VO2, but in this thread
I learned it was possible to make it look much better, so I went with it.
2) It's a lower price, about $50 less expensive.
3) Vance & Hines is the company Harley turned to when they wanted to get maximum performance from the XG750 engine, when they had them build the XG750R flat-tracker racer. I figured they probably knew how to get some good power out of my bike's engine, and being less expensive and (potentially) better looking, that sealed the deal.
If you prefer the look of the K&N, by all means get it, I think it's likely a very fine product and will give all the performance benefits it claims.
oddly enough, it gave my exhaust a deeper tone
Agreed. It sounds fantastic, especially when you have to go WOT, it growls like an angry tiger.