My apologies - I didn't mean for my post to sound sarcastic. The BDX valve is fixed at high port settings, and I suppose in a drag application they work fine. But, this significantly narrows the useable powerband of the engine, and pretty much every manufacturer is trying to build the best of both worlds (an engine with a broad powerband, which is why variable exhaust was invented).i don't want to reduce power or increase fuel consumption that is why i asked if they work. i am new to cat and i have been looking at different aftermarket parts and came across the BDX valves. I thought that BDX made a good product and these caught my eye. Thanks for the info, i will not waste my time with these.