2mm will make the different already. More air to go in to the air chamber and combusion room. That's why some bore it until 64 or 67mm... After market TB like Jun is 70mm at inner diameter. But bigger doesn't mean better, big enough for ur engine OK lar. Don't tell me a stock b16a is going to put a 67mm or 70mm TB.
G' day fellow ZTH forummers, it's been a while since I posted on the FI section of ZTH and just felt that I had to, just to share my personal experience of the above topic and I'd like to declare my purpose is not to...