Indeed. That is exactly what it is. You have what is unofficially referred to as a "DNA Stage 1.5".

The Stage 1 is the cylindrical main filter, Stage two refers to the replacement airbox top (no snorkel) and you have the restrictor ring fitted. This setup is generally accepted to be as far as you can go with the stock fuelling.

XTZ DNA Air filters Explained

Here's what DNA filter options you have available. As you move down the list, you get more air flow and there will be a greater need for fuelling adjustments:

http://i864.photobucket.com/albums/a...psd70ee438.jpg = Stage 1

http://i864.photobucket.com/albums/a...psd70ee438.jpg + http://i864.photobucket.com/albums/a...ps2405aad2.jpg = Stage 2

http://i864.photobucket.com/albums/a...psd70ee438.jpg + http://i864.photobucket.com/albums/a...ps2405aad2.jpg + http://i864.photobucket.com/albums/a...ps8177080e.jpg = Stage 3

With a stage 1 filter only, there is no need to adjust the fuelling, the ECU will cope with the change. However, as the XT already runs on the weak side of what's acceptable, you won't maximise the potential of the increased air flow without adding a little more fuel.

The stage 2 requires a Kev mod or Power Commander to richen things up, or the motor WILL run lean. There are a good few horses to be released from the stable with this filter and a correctly set Kev mod.

The stage 3 increases air flow further and requires even more fuel, but with further benefits in terms of horsepower.

There is also a restrictor insert available you can fit in the Stage 2 top cover to enable running the Stage 2 setup with standard fuelling...

https://images-eu.ssl-images-amazon....SR160,160_.jpg

Wow thanks Pleiades, I appreciate this explanation so much! Ok so then I definitely have the stage 2 and the below insert restriction hence having the ability to run the bike in factory fuel settings.

https://images-eu.ssl-images-amazon....SR160,160_.jpg

I am in dire need to get rid of a terrible surge on lower revs, it drives me crazy in thick sand and a few times almost threw me over the steering wheel when the engine will simply just surge or act weird. After some investigation I realized that its to do with the lean running engine.

So would you mind if I pick your brain for more questions;

I ride a 2014 XT660Z

If I remove the air restrictor, I will have a DNA stage 2 air setup (also have a aftermarket free flowing exhaust). I have purchased the kev mod book and will be building his fuel mod myself from the instructions therein, living in South Africa (weak Rand) its simply too expensive for me to import it.

Here are the questions that confuses me;

1) What on earth is the O2 Eliminator mod and what does it eliminate I read something about open loops and close loops?

2) Do I need to install a O2 Eliminator mod with the Fuel mod in order for me to set the bike richer on a Stage 2 DNA air setup?

3) At some stage my biked threw out dark and rich fuel smelling smoke puffs on acceleration which indicated richness, I took it in and they set the bike through the F1 CO tool leaner, the puffs stopped. How will this effect me, should I take it back to set it richer again also is it true that that only sets mixture for first 12% of throttle?

Thank you in advance, I appreciate your time and patience with me, and if I missed a obvious post somewhere explaining these things, I profusely apologize!

An eliminator does exactly what it says: it eliminates the O2 sensor from providing the ECU with any information. Catch is, they don't work! The ECU needs a signal from the O2 sensor to function properly.

The only O2 sensor mods that work are Kevs O2 Controller and Dynojet's O2 Optimizer. Basically these plug into the loom between the O2 sensor (in the header pipe) and the ECU. They modify the signal the ECU receives from the sensor when operating in closed loop mode and fix the air/fuel ratio to 13.6:1 as opposed to the rather weak 14.7:1 without any secondary control of the closed loop (stock). Closed loop operation (put in simple terms) is when using up to 3000ish rpm, small throttle openings and when cruising. As soon as you wind open the throttle the ECU works in open loop mode and disregards the O2 sensor signal.

No you don't "need" one, but... TBH, an O2 Controller (not an eliminator) on its own will make a huge difference to low rev flexibility and reduce surging. It makes the whole motor smoother revving and more tractable. Combined with a Kev mod to control the open loop side of the fuelling, you'll have all ends covered and a smooth 13.6:1 A/F ratio all the way through. With just a Kev mod fitted alone you'll have a bit of a jump/step in fuelling between open and closed loop modes where there's can be an sudden transition between the 14.7:1 closed loop and 13.whatever:1 set on the Kev mod.

Firstly the CO setting only affects <2% throttle, not 12% - tiny throttle openings. My guess is someone cranked up the CO to compensate for the filter/intake mods without realising that the adjustment only affect tickover and the first few millimetres of throttle movement. A CO setting that is a lot higher than standard will make surging worse. Sounds like this issue has been put right.

Thanks so much Pleiades, I will save this for reference, now I understand. Btw the Dynojet Dynojet's O2 Optimizer is not obtainable anymore it seems. I am just going for the mods then. I appreciate the feedback!