I have a 1800c with stock unmodified exhaust. I found another stock c exhaust and am in the process of removing the cat from the front of the muffler. so far I half about half of it removed. I was suprised to find it is at least 6" long. Will take some pics of before, during and after so you can see the design of the muffler which is what I was curious about...I dont want to drill out the back of the muffler. I suspect removing the cat will give a noticeable increase in volume but not be too loud. I am no engineer. The Honda engineers that designed this muffler know more about sonic waves, reversion, backpressure, etc. than I do. I am sure they used a high flow catalytic converter since it is so long. I expect to enhance the stock sound without making it sound crappy. The beauty of having another stock muffler to work on is if I destroy the muffler or make it sound crappy I can always put the original back on lol I will try to find a db meter so I can record the actual difference at idle and mid rpm.