Greg, no need to use a sarcastic smiley , you are going at it from a flow stand point and I am talking about an increase from stock flow versus sound level stand point. If this pipe is modded and used for racing, at least where we race here they do sound checks, removing all the baffles or drilling too many holes will get you thrown out of a race for sound infractions. For flow purposes the pipe #1 in Dodjy's pics is 1452 mm2 #2 is 660 mm2 #3 is 314 mm2 #4 is 227 mm2 and the tail pipe is 314 mm2. Drilling 1/2'' or 13 mm holes(154 mm2) through the baffles increases flow slightly , but also increases sound. So if you are being anal, then all mods should be done using a sound check to verify that you haven't gone out of limits. All I was saying is that I should have only drilled 2 holes to stay with in the sound limits a little better, 3 holes is just over the 96 db limit for our races here, and yes I have fashioned a 43 mm id tail pipe the same as Dodgy did. WR Dave.