Triumph used that combination (3134 on intake) from late '50s until about '66 on 650 engines. They used it even later than that (to '69 or so ?) on some unit 500 engines.
A 3134 on the exhaust too would make more power at high rpm, but it could make less below 5000 rpm.
A 3134 on the exhaust too would make more power at high rpm, but it could make less below 5000 rpm.