I just replaced the filters on my Injen long tubes with K&N air filters.

K&N PN - RU-3580.

K&N says these are the same size as the Injen filter replacments. The K&Ns are larger. They will however fit. It's the bottom larger end of the filter that is about .5" larger in diameter.

Notes.

1. Remove the bumper. Do not try to do this from the top opening where the hood latch is, and the undershroud is being blocked by the power steering cooling to put the filters back in.

2. The driver side filter will go in without issue. The fit will be a bit snug.

3. The passenger side filter will require you to remove the pipe between the filter and the rubber hose. Attach the pipe to the filter and carefully push the filter with the pipe attached into place. Reattach the the pipe.

4. The reason you have to remove the pipe is because of the horns. I loosened the bolt holding the horn bracket to move the horns to the right (left as your facing the vehicle) a small bit. Maybe 1mm or so, but it barely moved.

The reason I went with the K&N filters is because of the price difference. The K&Ns cost about $10-$30 less than the Injens. Now the reason I don't have pics is because I recently broke my camera. If you've installed these yourself, then you'll see what I'm talking about. If you got someone to install them for you, then refer them to this thread.

This may work for the Stillen LTs as well. I don't actually know as I have no experience working with the Stillens. If it does, feel free to post it here.

I got my flame suit ready JIC.

 

I believe the stillen kit already uses K&N filters.

 

If I was going to replace the filters, I'd go ahead and buy the AMSoil DryFlow filters that K&N now ships with their CAI kits. You can get them from AMSoil directly. Just my two cents.. since I prefer dry filters to oiled ones.

 

Thanks. I'll look those up next time around.

 

Correct the Stillens come with K&N's. I, however, replaced them with aFe Pro Dry S's. I can't stand doing the whole 're-oiling' thing.

Here are the part numbers for Stillen Gen 3 filter replacements:
K&N = RU-2820
aFe = 21-30003 (this was my own decision, based on cross-referencing the part lists)

The RU-3580 that th OP mentions will be a much tighter fit due to the 6" base diameter. The 2820's that come shipped with the Stillens are a 5" staright, rather than conical.