Yeah I know, being a convertible likely mainly used on sunny Sundays, the previous owner probably thought it would be ok to just let it self-ventilate.
I’m planning to make my own hoses, the thinner to the elbow is pretty straight forward while the thicker to the intake is tricker containing the check valve and filter/restrictor.

To be able to pick the later, I’m locking for roughly what vacuum it should be at the end where it hooks up to the Opti, thinking that too much vacuum wont be good for the opti either

there is a vacuum restrictor on the suction side that won't let to much air through. gotta have that.

well it is cheaper but shipping will kill you https://petrisenterprises.com/produc...vacuum-harness

Thanks for the tip, that’s the best price on such harness I’ve seen so far

You are spot regarding the shipping cost, added to that I pay 25% tax on the total (parts and shipping), and with a currency down the drain as mine, it gets expensive, what saves me most of the time is that parts for US cars often are cheap

I’ve been searching on the net for the orifice/filter as a separate part, but it seems unavailable, and maybe it never was available
From my understanding it serves two purposes, restrict and keep the air flow clean

Knowing the expected vacuum at the Opti would help to pick the correct components that probably are cheap.
I'm hoping to find the ref value for vacuum on a Opti data sheet somewhere or in a FSM for 95-97 GM with vented Opti, my car is tucked away over the winter, so I’m in no hurry :)