Okay, disclaimer first...
I have no proof that this modification will not do harm to your engine. I have no proof that this modification gives any substantial gains in horsepower, torque, or fuel economy. I have no proof that I have no proof.
That being said, my thinking was: the more that is in the way - the more restriction you have.
From my understanding the secondary air filter in the Tacomas is a charcoal filter to reduce vapor emissions from a freshly shut-off engine. This makes sense to me. It is a charcoal filter. It just doesn't seem to do much else but cause air restriction. So, here is how I took mine out.
Please pardon my filthy truck.
NOTE: This is for 2ND GENERATION TACOMAS ONLY! This section of the tutorial is on a 2.7L inline 4 cylinder engine. For additional pictures showing the 4.0L V6 filter removal CLICK HERE.
You will need:
1) Flat Blade Screwdriver
2) 9/64 Drill Bit
3) Electric Drill
4) 6" x 6" piece of Aluminum Foil
The easiest thing for me to do was remove the upper air box assembly and take it inside.
To do this you need to unscrew the bolt clamp on the intake hose, and you will need to remove the plug to the MAF (Mass Air Flow) sensor. The MAF plug also has a clamp that is mounted to the upper air box. You can pry it out gently with the screwdriver.
Once I removed the upper assembly, I used the aluminum foil to cover the intake tube.
THIS IS IMPORTANT!
The air filter prevents dirt from getting into and scoring your engine (very bad). Without the assembly and filter any thing smaller than 2" can get in there. So, cover it up and protect your investment!
Next you will want to use your drill and bit to drill out the 6 plastic rivets that keep the secondary filter in place. BE CAREFUL NOT TO DRILL TOO FAR!!! You don't want to go to the dealership to ask for a new airbox - it will ruin your weekend.
Once you have the rivets drilled out, you can use the screwdriver to pry out the filter. Once the filter is out you can see that there really isn't much to it.
AGAIN: TO PROTECT YOUR INVESTMENT - MAKE SURE THAT THE AIRBOX IS CLEAN OF DEBRIS AND PLASTIC SHAVINGS BEFORE REINSTALLING!!! THIS IS A MESSY PROCESS AND SHAVINGS WILL BE EVERYWHERE!
That's it! Put it all back together (minus the secondary filter of course), and you are good to go!