Well, you probably already got clued in that it looks to be the oxygen sensor. Also, you should check out Ebay for a company that seems to be selling an intake for the Rav4.2. Looks like they took out the airbox completely and attached the intake to feed directly into the manifold. But for some reason, I can't seem to find their O2 sensor mount. Oh well. If you are making custom 4.2 CAI's, maybe I'll hold off on the Weapon R Secret weapon intake till I see what you guys come up with. Hopefully, you guys can get it dyno tested just so we can see some actual numbers. I hate it when other companies give you a vague idea as to what your hp gains will be so you're left wondering if you'll only get 5 or 10 hp gains for some mod.
The intake we're thinking of making is similar to the ebay one except we have to work out what to do with the oxygen sensor (as you've already stated).
If we successfully make a sports intake for the RAV4.2, we'll offer 2 versions. One with an open pod filter and the other wilth an enclosed pod filter with a cold air pipe running up to it from down low. The intake kits will be tested on RAV4.2s before we release them for sale. We'll keep everyone updated on our progress.
It's called a Mass Airflow Sensor, and you have to be careful with it because they can be easily damaged, and they cost a couple hundred dollars to replace. It measures the amount (actually the speed) of the air entering the intake manifold. That's how the ECU knows the amount of fuel to inject.
Also, I shouldn't have to mention that a MAF sensor is required for the engine to run, so it's not something you can leave out.
If you look at some of the mass produced CAI's that fit such other Toyota cars as the Celica, they have a mount built into the piping specifically for the MAF sensor. That's why some of us have been able to take Celica CAI's and rework them to fit in a 4.2 Rav.
Anything other than a TRUE cold air intake is crap (such as those short-ram ones on eBay) and will not improve anything, just the bank account of the guy who sold it to you. To have an intake that makes some sort of improvement, you need it to extend to at least the headlight area, or preferable down into the fender, with some sort of heat shield (like many of you guys have done).
If you guys down in OZ are able to fabricate a true cold air intake I would be thrilled and love to get one, although I don't know how much the shipping would be to get it to the other side of the globe.