Do you use the KN on your RX7 (What year? 12A, 13B?)then and have you been steadily?
I've got an 88 vert and have used pretty much Mazda stock and recently the Purolator premium filters. Use those on the Cougar and the other rolling stock I've got.
I've never noticed a problem on the RX and its now got 224,000 miles on the stock N/A motor.
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