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.
wanna change my tyre for quite a while d, cause i've been using it for more than 3 years, now my tyres always will come out with some noise, make me worry cause i feel insecure when the sounds come out while driving...