Adapter

34mm is the engine side of a 34mm carb, the back is 2.25" O.D.

i run this 2.5" x 2.25" silicon intakes boot from my 2.5" cfm box to the back of my 34mm PJ @ 2.25"

Pipe Reducer

get the clamps from them too, they rock for the $, way better than standard radiator hose clamps.