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.
Can anyone teach me to DIY the fishbone boost controler. Which one i should connect to??? If possible show me pic it will be more detail. For youe infor i'm driving mira L5