The Yaris got a fun new part last week. I ended up picking up a Micro Image high-performance intake manifold as well as a larger throttle body off of a 1ZZ-FE engine (e.g a Corolla), which is not generally included with the manifold. This throttle body is significantly larger than the 1NZ-FE throttle body and allows for more airflow, which means more power and throttle response.
Installation is pretty darn easy; it helped to have a buddy who had done it before, too. Disconnect the battery, unbolt the stock plastic intake manifold, unclamp some hoses, swap over the black box with the chip from the stock throttle body (this will require drilling out the rivets, then re-riveting it onto the 1ZZ-FE manifold), and bolt it all back up. The most difficult part is the chip swap, but it's not too bad. Then again, my buddy did this part for me. It's good to have friends.
I started up the engine and it did a bit of searching due to the computer recognizing the new parts. Even now, my setup now has a high idle (about 2,000 RPM) for about a minute, then it comes back down to about 700 RPM like normal.
The gorgeous looking aluminum intake manifold features long runners, a large, square body, and is said to make 7 hp and 7 ft/lbs of torque on a dyno—I believe it. Above 3,300 RPM, the engine feels as if it has woken up. It's quite noticeable when going up hills or passing. It simply feels more alive, and doesn't feel as if it's running out of breath in the upper ends of the powerband. I didn't notice much difference in sound, but I wasn't expecting to.
I did have to space out the radiator hose a bit, as it was rubbing on the leftmost intake runner; I believe the brand-new part has a spacer (I made my own). Also, the stock engine cover won't fit without a bit of minor trimming, but I'll eventually get around to it. Or I won't, and I'll leave it off; it looks kind of good without it. Other than that, this is a masterpiece in metal, and looks fantastic.
I'd recommend this modification to those looking for something to bring the car's drivability up a notch, especially if you've already done the basic intake, header, and exhaust modifications.