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.
Guys, I know I don't belong with you 4G6X engines
But something is very wrong with my car.. I'm lacking a lot of throttle response for a 1.8, and my throttle fuel consumption is quite high.. I'm not sure...