Sorry off topic.
But another good alternative to BT is open throttle but with a bolt-on air filter on each.
You can get suitably sized air-filters from any good bike service centers.
Or you can opt for full K&N filters. I saw Eneos got small sized ones that can fit the throttle diameter.
When opening the surge tank don't be surprised to see 4 funny intake pipes. Just remove these and slap on the filters and you should be fine.
Budget for some samco hoses as well if you like... If only for the sake of looking professional.