between this site and 6mt.net i have come to the conclusion that the Ztube and K&N filter are a gread mod for 03-04 sedans, but aren't really worth it for 05-06 sedans.

i have an 05 sedan and was thinking about getting both the Ztube and K&N but now think i should just get the drop in k&N.

what do you guys think? i know this is discussed a lot, but have there been any conclusions.

why not a cone type air filter? anything should be better than our stock air intake unit, but no crazy gains only like 2 -3 hp

I think the stock unit is well designed on my 05'. It takes in cold air from in front, not under the hood. It has a water drain and plenty of surface area. I put in the Z toob and K&N because I got them cheap (new) from one of the members here. I DON'T think it made a bit of difference except for the noise from the intake has a lower growl.

For the most part, I also believe that Z tube in itself will not afford much. However, when the said is coupled with a plenum spacer and the like, I personally think it does help. No justifying data for my comments . . . Just my own personal take on the deal.

Shameless plug, but related. I had the K&N in for less than 500 miles and switched to the Stillen. Like new, $30 shipped for anyone that wants it.

Ditto. The sound is different, and that's about it. Worth it if you get it cheap.

I put the Z-tube on my 05 simply because it is a cheap easy mod and I like the growl it makes when you get above 3,000rpm. You do not notice any seat of the pants difference, but it has to make it a bit freer breathing when you compare the stock tube with the z-tube. I would not bother with the K& N drop-in filter, I would stick with the stock filter or, if I was to change the filter I would go with the Stillen cai.

It depends on what you are expecting. With a more open CAI, it does deliver a more aggressive sound. Performance wise, I doubt it helps much but it doesn't hurt either. I also think it's worth the investment to get a K&N filter because it's reusable.

i have a z-tube on an 05 AT and it sounds better, no performance change that i noticed though

save your $50 toward a mrev, i just put one on my 6mt, no sound difference whatsoever, but it made the car smoother. here's my thread:https://g35driver.com/forums/g35-sedan-v35-2003-06/88364-z-tube-installed-05-6mt-impressions-questions.html

good luck,
benjamin

I am starting to think that this is true because of the differences in the intake plenum (revup plenum has shorter runners). But after you change your plenum to a non-revup (i.e. MREV!) and add a spacer, that ztube K&N should do the same thing it did for the 03/04. At least this is my hypothesis based on these forums.