Save money and get a 3" custom.
look on the vid on the last few posts of my b20 build thread - thats a QUIET 3" lol
I have a 3" system sitting in my cupboard if your interested. It is straight through though.
Am actually getting it at a good price but dont want it to be stupid loud
For racing it will be fine, for trackdays you will need to run the bung on the 70mm and 76mm.