i'll take it off your hands if you dont want it. ;] I've been wanting to try one.

ive got a v1 sitting in my garage ill sell you cheap if you want it. its a bit dirty but i could clean it up. lmk

sorry i already installed it or i would

So is the K&Ns statements about the power increases completely false? I thought they said if thats the case they would refund you?

I got a K&N v.1 for free and put it on (would have left the oem airbox, but MAF sensor screw fittings were stripped so it was just kinda sittin there, plus I needed a new filter anyway..). It's alright. It sounds pretty sweet, but there are no gains or anything from it. I haven't had any idle issues so far, but it's only been a day. I don't plan on keeping it very long though, because of everything I've heard about them. I'll probably either go MS or AEM when the time comes though.

I put the MS CAI on both my 2008 40th Anniversary Edition RX8 and my 2008 Mazdaspeed3 GT. Love the results with both. The MS CAI and AEM CAI are the same part, the only difference is the MS CAI will keep your Mazda warranty intact.

Of course I get much more performance improvement on the Mazdaspeed3 GT, as it has a direct-injected turbocharged engine.

In tests the RX8 with AEM/MS CAI can gain anywhere from 5-13 hp . ( that varies and depends on ambient temp and humidity ).

I have driven all types of rotaries, stock, turbocharged, supercharged etc. while owning seven rotaries since 1973. The MS CAI was a relatively inexpensive and safe way to gain a little more speed, better throttle response and better overall breathing in my RX8.

Many here will pooh pooh any CAI, but if you drive an RX8 without one and then drive a real CAI-equipped one , you will know the difference. The lower and more forward positioning of the intake in the AEM and MS-type intakes gives you cooler air than the shorter ram-style intakes, no matter who makes it.

Some will caution about water ingestion fears with these types of lower intakes. But they come with a sock and unless you are driving through constant massive puddles, or fording streams, it won't be a real problem. A small amount of moisture gets into any intake system, and is no real danger to your engine. Huge amounts of water ingested could be a problem. The track record with these products is mostly good. I drive in the rain, through occasional puddles, and use an automatic car wash, even in winter, and I have had no problems.

I had a true CAI for my 2005 Mazda3. I ran through an unexpected puddle on an expressway ramp at high RPM in third gear and sucked up enough water to short my MAF sensor. I spent $600 in parts, labor, and rental. I will never again use such an intake, at least not without a "sock," but then I wonder, how much power am I losing to the sock? I asked K&N that question back then, and I got back, "Not enough to notice." OK, but how much is that? 3 whp is probably not enough to notice. So, let's say the intake without sock nets 8 whp more, but I lose 3 of that due to the sock. Now I'm back down to what I would likely see from a safer alternative, and one that is easier to get at for cleaning (and quieter). Without harder numbers regarding how much power is lost to the sock, I'll stick with safer, quieter, options. If someone can show for certain that using the sock results in no more than say 10% power loss over the sockless setup, I suppose I would consider going with AEM.

A CAI in a Mazda 3 is not the same as a CAI in a RX8. The RX8 AEM and MS CAI are designed for the sock, the hp numbers from AEM testing are WITH the sock and are 5-13 hp (depending on ambient temp and humidity ) . And most folks love the sound these CAI give. If you want quieter, don't get a CAI.

No one who buys a AEM or MS CAI is running a sockless setup anymore unless they took the sock off. They are designed now and come with the sock standard.

OP, if you can find a used RB intake or a good deal on a used one, go for it.
I personally got the one I just installed on my car for dirty cheap from my local junkyard ^_^ (who knew some people just send totaled cars with mods on them straight to the junk, got my aftermarket radio/metra from them too).
Junkyard didn't know that the RB intake and metrakit+doubledin was aftermarket so I got a good deal on all of it.
Anyways, install was a bit time consuming but I loved how it sounds from 3500 rpm inside and from what all my buddies tell me, it sounds awesome on from the outside as well. Better throttle response too.
For the risk I took of buying it with unknown mileage and such, I think it was one of the best buys.

AEM's website lists the sock as a separate accessory.

Mine has no sock, It's the old AEM (not K&N) version. But I only bought the AEM to go with my Turbo Kit. If i was staying NA, the factory intake would stay.

As i noted, if you buy a NEW AEM or MS CAI, they come with a sock now as standard. AEM lists a sock as a separate part for those who have older units that had no sock.