As some of you know I removed my cat and resonator a couple months ago and posted the results " AF ratio change" I said then I felt that the mid range had pick up a bunch but the bottom end was a little off. I did report that the Af ratio under full throttle was still rich, 11.6 to 11.8. Well after installing a Dobeck tuner 3.5 version that was loaded with a program for a aftermarket exhaust what a difference! I use a area of about 400 feet for all my testing" small drag strip so to speak" and with a little tweaking on the Dobeck tune I have picked up 3 MPH in this 400 feet and man dose it pull on the top now where as before it just felt flat. Under full load it is now at 12.4 to 12.6 on the Af gauge. As for the bottom end it is getting much better and I think a little more fuel and it will be good. So clearly the stock 11.6 to 11.8 is a little rich for max performance. 12.4 -12.6 is still very safe for a NA motor. If I had a dyno near by I would have had the before and after results. It makes one wonder how close this would be to a aftermarket exhaust, close I bet even through the stock mufflers. We need someone to build a cat delete and do some dyno testing, for the exhaust company's there is no money in that.