is't on the intake track you cant miss it.
it there to tell the ecu the temp. of the incoming airfor fuel mixing

 

I think I will build my own. Can't decide between a short ram or CAI? Anyone have any suggesions?

 

x2. I've never understood why people pay so much for short ram intakes- they're so easy to make yourself.

The bad thing is, your gains with a short ram (cone just chillin in the engine bay) are going to be minimal/none- that hot air its sucking in isn't helping. The other bad thing, is with the 5th gen's- your battery/windshield washer tank are right in the way for doing a FWI (extending the tube into the fender). Its doable, but you either have to turn or relocate the battery. A CAI would be better too- but since no one makes one for your car, you'd have to do a short ram, and build your own insulating box- which isn't the easiest thing to do if you're not used to building stuff from scratch.

It is the IAT- measures the temperature of the incoming air to more accurately dial in timing. If you look at the rubber elbow on the stock tubing, you've got two electrical items. One is a big round piece that the tubing attaches to- the MAF (measures airflow coming in), and the other is a little round plastic sensor stuck in the side of the boot- thats your IAT. When you build your new intake, just drill a hole in the side of it (make sure you get the shavings out)- go to Autozone with your IAT (it just pulls out) and get a rubber bung, like a PCV bung that snugly fits your sensor- and install the bung into your intake tubing, and press in your sensor.

Honestly, with a 3100- you really have to think ahead about what your goals are. I did exhaust, and a short ram (HAI) on my 3100, and it still ran within .1 second in the 1/4 of what it did stock (well within margin of error due to weather and such)- so I had $300 or so wrapped up in an engine that didn't feel faster, and didn't really run faster.

There are mods you can do to make more noticeable power- but there are no real cheap, big hp mods for the 3100 other than nitrous. The 3400 top swap is getting pretty common, and isn't terrible to do- but in the end, you really have to consider how much money you're spending on an engine thats probably always going to be stuck in the 16s in the 1/4 in full street trim.

I'm not trying to turn you off from modding your car, or trying to convince you to do an L67 swap- but with how expensive it is to get the 3100s to run noticeably quicker- I'd personally just find the exhaust setup that sounds best to you- and just leave the rest for reliability.