Hi again mate,
But do you think that partially blocking off 'all' the ports could be a workable solution here?

So in full, restrict the venturi, main side transfers, bypass and exhaust because this is what a purpose built diesel would do.

And I am most curious as to what a tapered wedge of timber would do if used in all 3 transfer ports instead of simply blocking the boost port off completely.
My hunch is that leaving the gas flow pattern as intended by the manufacturer but to a lesser extent would be the way to go IF you can get those ports partially blocked in a permanent manner.

Itoo have used a piece of spruce carefully shaped as to jam tightly into the entire boost port and my fear is how would one tightly jam anything into part of the port?
A partial piece is not going to be as supported as a full piece of timber and it could move around in use, so perhaps JBweld glue to the rescue?

Talk soon, Chris.