I don't know the numbers but on flowmasters site I think they have a number chart on there... Anyways they have the hooker mufflers from 2"-3". There's two different ones... The Aero Chamber which is supposed to flow up to 441 cfm of exaust gas and then there is the Maximum flow that flows 595 cfm of gas. So looks like the Maximum one would be something you are looking for. Also check out Dyno Max, I hear lots of good things about those and they sound pretty good as well. I see a lot of Edelbrock mufflers too but they are mostly for street applications and flow about 116-200 cfm they say. Borla is another brand to check into. For my car I am thinking about going with Hooker mufflers but I wan't to check out more before I just go out and make a choice. Your best bet is to try and go on each site and see if they have a flow chart or anything. If not then just pick a brand and go with it.