Am thinking of springing for the K&N system for my 06 V-6 Taco. From what I've heard, they do seem to provide a noticeable increase in power. Again, from what I've heard, the main drawback seems to be the risk of oil from the reusable filter causing problems with the oxygen sensor.

How significant is this problem? Can it be overcome by reasonable care not to over oil the filter element, or maybe by buying a second element, so each element could dry thoroughly before being re-used?

Are there alternative brands that solve this problem or provide superior performance for my engine?

Finally, headers seem to be the recommended second step to harmonize with increased air intake. What brands would you people recommend? TRD? I want a system that will work with the existing cat and single exhaust.

My goal is a power increase of around 10% without major mods, or voiding the factory warranty. Any general observations along these lines would also be appreciated.

Thanks!

Well, as far as the K&N is concerned, I believe the cons outweigh the pros. It does let more air pass through, but also lets more contaminants in as well (not to mention the MAF clogging problem, which I've personally dealt with).
I have had really good luck with the AmsOil air filter. It's a dual-stage sponge-type filter. It traps more contaminants than a K&N (much more) but allows almost exactly as much airflow in as the K&N does. There was a website that did a dyno analysis of the two, but I can't remember which one (www.gadgetonline.com maybe?).
Also, I've heard that headers do help to some extent, but unless you plan on supercharging your ride, the only major difference is the sound (the stock headers are very well designed as it is).
Hope I helped! <img src="/forums/images/graemlins/kewl.gif" alt="" />

Oh BTW, I just saw that the truck is an '06. You might have a MAF sensor located farther back (eliminating the clogging problem), and am not sure about the headers on the new models <img src="/forums/images/graemlins/baby.gif" alt="" />

But, I do still stand behind the AmsOil filter, they are great, and reusable. And, at about half the price of a K&N, it's worth a shot!

I have had the K&N FIPK on my 2004 for 2 years with no problems. I would look into the AFE intakes to see if they have one for you. They don't have one for my 2004 2.7. But like I said I have had no problems with my K&N. I do have the Drycharger on it.

The 4.0 has a pretty impressive intake system from the factory. I have the K&N replacement filter in mine and have noticed no appreciable or noticeable gains in performance or efficiency. The 3 to 5 HP gain you MIGHT see from an aftermarket intake kit will not be something you will notice, IMO.

Trying to find a 10% gain is not likely to be anything you will be able to perceive and would take more than an intake and an exhaust on the 4.0 The engine is already optimized and has the VVTi and intuitive electronic management. Drive with your foot in it all the time and the engine will always respond as such. Wait until you have burned up the warranty mileage and install the URD supercharger kit.

Headers, JBA. The exhaust system would benefit from a freer flowing muffler, but the tubing is already 2.5". Cat-back kits will add the muffler and look fancier, that's about it...

The dealer will almost ALWAYS point at aftermarket parts as being the cause of issues, caveat emptor.

Thanks guys! Interestingly diverse opinions.

If the 4.0 is fairly well optimized from the factory, it does stand to reason that there will be few, if any "simple" mods that will yield significant power gains.

Will do more research before taking any action.

URD offers a y-pipe, which removes the 2 rear cat's (still leaves the front one) and a 3" stainless exhaust.
They also have a computer tuner that you can get 15hp+ with (thought you need a wideband to tune)....
check www.customtacos.com for 4.0 mod's... lots of xrunner owners there.