I got an aftermarket muffler (used Jardine GP1) but it doesn't have the bung. Like your saying most of the weight of the factory system is due to catalyst and noise restrictions in the muffler. The factory header is thin wall stainless pipe but has a steel crossover (??) and the fabed up collector where the pipes come together is steel too. Not too heavy for a factory peice. I wanted to keep the crossover for now. I know on the ZX7R's it makes a big difference in the midrange. I think no crossover is good for high RPM though. You couldn't beat the old super heavy steel factory headers on the 7's because of it. Cost a ton to get a good aftermarket (I got a Muzzy race) that had crossovers and then all you ended up with was the weight loss no more power.
I ended up welding the bung to the inlet side of the muffler instead of on the header like I was going to at first. Should have it back together today.
I'd like to try an arrow header or Leo Vince some time thought to compare. There is some crazy looking Japanese system that has a resonating chamber on it (can't remember the name) that is supposed to be really good but I think they may have quit making them and they were REALLY expensive.
Last edited by juliozx7r; 05-16-2010 at 01:45 PM.