After my Ultra Flo muffler swap, I did notice that the exhaust fumes don't smell as rich as they used to with the Flowmaster muffler. Could this be due to the better flowing mufflers? Somehow allowing exhaust to exit more smoothly, thus increasing air intake and more complete combustion???

[This message has been edited by engine (edited June 21, 2005).]

The only way to tell would be to take intake manifold vacuum readings before and after the exhaust swap. A restricted exhaust will cause manifold vacuum to be lower, where as a free flowing exhaust causes vacuum to go up. If everything else stayed the same then the increased vacuum would draw more air in thus leaning out the air fuel mixture slightly.

thanks. I'll do that. I know I usually run about 15" or so.