Thumpage, Excellent info! I saw the photo of your reduced stock-drilled tip on Yahoo user group but made no sense until you pulled it together here. Key info re tip mating to internal baffles and how stock and HRC tips produce power/noise. How loud is it? beerjonny, So how's the db Dawg sound? It's been four hours already:) They have nice web page but not sure how it achieves the claimed 10 db sound reduction. PutteLiten, I've read another thread, AdvRider.com, where poster claimed FMF was not making Q4 for XR650R. abby, I have an RS db meter as well but don't know to use it for db measurement (only got it to balance my home theater system). Do you select '90' on the dial and add or subtract the meter reading to arrive at 95 db? Can we send all these modified tips to abby to get the standardized 'abby db rating'? It's seems we are all looking for the same thing and duplicating efforts. I already tried the stock & HRC tips and am now looking for a used stock tip (don't want to be without the original stock tip) to modify. Love the HRC tip power, cannot live with the sound. That is, my neighbors cannot live with it.