Sorry.
The mod is to stop starvation of the main jets from fuel moving away from the base of the float chambers. Also he details a lot on venturi diameters/carb size.
I'm not too sure just how critical the sizing actually is.
My 3.2 runs 50mm PMO with 36 venturies, way too be but runs fine now, (or rather did..)
My beef is with a specialist, some very poor basic machining work and the resulting after sales service, but it is behind me now, sorted things out myself, usually the best way.
I am not a fan of specialists unless I really have to use them due to special equipment or my ignorance.
Just remembered I should have bought the DTI gauge back from work.....
One day you will all get as old as me.















