[Vader]

This past winter I decided to change the air cleaner on my FE to one of those "Cobra" Oval style. They are readily available from Tony Branda, Finish Line, etc.among others. When I was installing it I noticed that it was a lower profile than the Wysco air cleaner that it was replacing. I did some quick measurements of the surface area of the element and since it was about 15% larger I decided that it probably would have, if anything, a small effect. Boy was I wrong. I put my car on the dyno this week and it had lost 33 hp. Most noticible above 4k with lots of black smoke
My engine tuner/dyno operator said he had seen the same symptons a couple of weekes earlier with an SPF that was running a 428 with the same air cleaner. We did some more pulls, with the orignal Wysco, the "Cobra" Oval, and no air cleaner. No doubt, it was the restriction from the filter.
The original Wysco is a 15 x 8 inch oval and has a 2 inch high K & N filter. The Cobra style is a much larger size- 20 x 9 but comes with a 1 3/4 inch high paper filter. I'm going to replace the element with a K & N style that's 2.5 inches tall and will re-test.