just an observation...........
Although I never installed one, I wouldn't for a few reasons;
1) Roof drainage. When it rains and you brake, tons of water drain onto the windshield. Having a deflector will allow "pooling" of water and a surprise waterfall when you open your sunroof up. Remember that a 4th gen's nose is "drooped downward" unlike previous generations. Water will naturally flow toward the nose when braking or after the truck has been sitting after it rains.
2) Keeping them clean. Debris/leaves can/will accumulate there. I've seen it many times on other cars
3) Wind buffering: I can't comment on this, but I figure why if the 4Runner ALREADY comes with an automatic retractable wind deflector (pretty neat if you observe it work).
My 2 cents............