I have installed a pair of K&N air filters on my XLR & have noticed that the car is slightly more responsive and gets almost an extra mile per gallon. Has anyone else tried this and had the same results?

I've been looking for the K&N for my car
What exactly did you install?

If my memory is correct, the right number is 33-2063-1

I don't have my owners package with me, however in the back there are part numbers for replacement air filters. If you cross-reference that number with a direct replace from K&N you will find the right one.

If you do a search of their website base on the car (04 XLR) you will end up with nothing.

The XLR uses K&N #33-2063-1, the same filter as the Seville & Deville. You'll need 2 filters.

I found the attached article regarding modifications to make the K&N application even better. Has anyone tried this?



I have found an easy "free" mod you can do to really help your Northstar breath better. It takes about 30 minutes with common hand tools. If you installed a K&N filter, this mod will help even more.
If you take your air filter out, you will notice a hole at the bottom of the air box. Believe it or not, this hole goes down to a "black box" that is COMPLETELY sealed. Go figure!? Not much fresh air coming through there. Go under the car, just in front of the driver's side front tire. Pull back the plastic liner that covers the bottom. Be careful when pulling out the plastic plug clips - there are two at the bottom front of the front tire's wheel well. Those should be the only ones you will need to snap off. Carefully pull back the liner. Once that liner is pulled back, you will see the "black box". Cut the bottom of the box out. I drilled a few holes first,
then used a hack saw blade and easily cut through the plastic. Sand the edges down smoothly. Once the bottom is removed, you will see the hole which leads up to the air filter. Finally, cut an approx. 8" x 6" hole out of the plastic liner directly under the box. GM was nice enough to give you an indentation to use as a template. Make the hole just large enough to allow the air to get up into the black box. Again, sand
the edges down smoothly. Carefully pull the liner back into position. Clip the two plastic clips back into place and you're ready to go! Optionally, I also removed the metal screen located in the throttle body to help further increase air flow
into the runners. But it's up to you if you want to do that.

Net result is that the throttle response is MUCH better and the Northstar really sucks some cool fresh air now. Also there is a great sound when you
punch the gas - but not overly loud or annoying. Good luck :flag

If I have some free time this weekend, I'll climb under mine and check that out.

If I have some free time this weekend, I'll climb under mine and check that out.


Sounds good, but I'll be waiting for your second opinion

I was under the front of the car a few weeks ago looking for signs of a coolant leak (never found one) and I don't remember seeing what the poster describes, but who knows. I do like my K&N filters though.

I like the K&N's as well, and have my exhaust to make it sound good, but it would be nice to get some extra air flow.

Thanks for the post jack

I'm not sure what vehicle this article pertains to, but it sure isn't an XLR. There is NO hole at the bottom of the air box and there NO black box below that.

As we all know, there are two air inlets on the XLR (thus requiring twp filters). You can easily see the air boxes by removing the filter covers. You will also note that the filter actually fits up inside the cover to the air box, therefore cutting a hole in the bottom of the air box would permit unfiltered air to pass into the engine - - not a good idea.

Have to agree, I double-checked mine and there is no way that modification would begin to work. Sounds similar to the air box modification the Lightning crowd has been doing for years. As an alternative to driving around with a large conical filter hanging off the end of the intake, they cut the bottom out of their stock airbox and install a K&N filter. On their S/Ced engines it is good for a measurable gain in bottom end performance.

Here's the response I received from K&N about using their filters in an XLR. Has anybody actually used their filters in an XLR? Is # 33-2063-1 the correct one to use and were any modifications required to use them?

Thanks for your feedback.

- - - - -

At this time we have not released a Replacement Filter for your vehicle. If you'd like to be notified if/when it is released for your vehicle, please visit our "product request" page at http://www.knfilters.com/products_needed/default.aspx and take a minute and fill out the form. You will be notified via E-mail when a product is released. (The system will automatically send you an e-mail with all current products available or confirmation that we do not have what you are looking for, and future e-mails will be sent if new products become available in the future).


Thank you,

Leon S. Collins

K&N Technical Support

1-800-858-3333

I'm using them in mine with no modifications other than installing the gasket they included in the box.

I'm using them in mine with no modifications other than installing the gasket they included in the box.


same here...

I've just installed them in mine. Only modification was cutting down the supplies gaskets... :flag

When you check the K&N website, they only list a Oil filter for the XLR.

The 33-2063-1 works fine. I understand that if you go to the K&N conversion chart and match the stock XLR filter, the 33-2063-1 shows a match :flag