I have been running K & N filters for the past decade. When I installed my filters, they fit fine. Over the years, though, the same shrinkage has occurred as depicted above. Today, I decided to pull the K & N filters out and go back to factory filters. I didn't really notice any loss of power with the newly-installed factory filters. K & N prescribes a high interval for cleaning their filters and I've always been a little bit nervous about that. It seems like 50,000 miles on the same filter is way too long.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles