So was looking up this to do for my Statesman and noticed the link for it was dead but managed to use a website to see if it'd been archived and it had so here's the instructions from the ls1gto site.
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Decided that it was time to have proper cabin air filtering. The only other solution I had seen was duct taping heater material over in air inlet. Not a "great" long term solution for me. So here is what I did - pics attached:
1. Remove screw/clips to lift up rain guard and expose the air intake for the cabin HVAC.
2. Remove the High Performance GM Wire Mesh "Filter" by lifting up on the clip on the front. Comes right off. You will now note that there is a shelf ready made for a drop in filter of the right dimensions.
3. Purchase the Fram CF8921 activated charcoal impregnated cabin air filter seen here next to the GM version.
4. Here is where it gets just a little messy, though not difficult by any means (if you can use scissors). The Fram might fit in nicely on the shelf in the inlet - but the back of the inlet tapers down to a "V" shape and the edging of the filter will not fit. After trying to trim frame and a couple of other attempts - I put the GM screen on it as a template and cut the filter to the same size (along the long side) and was going to glue the back piece back on.
5. After one trial attempt for size - I realized that the filter material actually conformed and pushed right in to the tapered area in back, and the other 3 sides fit perfectly. There is foam around the frame of the Fram - and it fits perfectly and holds the filter in place. As you can see - I also tapered the back edges a little - but that was only necessary on the Driver's side - so do it there.
Just a few more showing how nicely this filter fit in. It is a very good fit indeed. I tested with full fan power - and it was drawing in a lot of air! But not a bit of buckling in the filter.
Also - You can really smell the "fresh" scent of having charcoal filtered air.
Personally - I am looking forward to having less dust in the car, which seems to return within days of cleaning up the interior!
Hope this helps the group. Install is easy, results perfect, and I can replace/reinstall at any time.