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.
Hi ppl...my name is Fazid from SIC...we are currently updating our database on all the car clubs available here in malaysia for the purpose of our future event which is the MME and the coming Moto GP...appreciate if...