After reading every post, it's quite clear gains can be had by up'ing to 2.5" piping, to 58mm TB's and larger IC's. I've got the 58mm TB's and Z1 IC's and plan to get 2.5" piping but I'm curious as to how (or even if) the GodSpeed SMIC's have been compared to the massives as part of a complete package. I'm sure my GT675's could use the extra help and from what I understand from the above and might reduce the spool up as well.