Well I got my mac prochamber on today. And it's not quite what I expected. The sound is a little deeper but it really just rumbles more. It's not really louder at all. And I have read anywhere from 10-22 horsepower gains from various sources but I don't really feel much difference. I kept the stock mufflers and am hoping that is the problem. Is it possible that it's leaking? I thought that might be it. I'm thinking of ordering some flowmasters or maybe even the illegal route and buying some dynomax bullits. Any ideas?