D-Jet vacuum hose question, Which hose, or Both? Options

[Olympic 914]

Just finished up installing all the FI wiring harness and the vacuum hoses and now the engine compartment looks like a bowl of Spaghetti.

This engine started out as a 73 1.7 with the stock FI and I converted everything to a 2.0 system. I did use some of the original 1.7 parts as they were the same for both engines. But all the 2.0 FI parts ( throttle body, plenum, air filter housing ,etc.) where cobbled together from fleabay purchases and I am not sure what years those parts were from. Also used the original 73 1.7 FI wiring harness and ECU and had to make a couple extensions to get everything to hook up. Not much problem there, (except for trying to connect those ground wires under the plenum. )

Now to the question, I was using Bowlsby's vacuum diagram that is for a late 74 2.0 system and while hooking up the vacuum lines to the dizzy it seem that one line is no longer used.



in the diagram above I have the green vacuum hose connected from the throttle body to the dizzy as shown by the Orange circles. I also have another vacuum port on my dizzy that I have connected to the second vacuum port on my throttle body shown by Blue circles.

Should I have both of these hooked up? or do I disconnect the Black vacuum line as shown in Bowlsby's diagram and just plug the second port on the throttle body.
This is what I have hooked up now.



Is there a reason that the later versions did not have this second port hooked up?
What benefits are there to using the second line to the dizzy vacuum canister?

in picture below the green line from the throttle body is routed differently

[wonkipop]

pay attention
@hndyhrr
@914sgofast2
@JamesM
this is a very old thread, you are responding to the wrong person back in time.

@Stratfink is coming in on old thread and asking a very specific question about vac lines from the distributor to the throttle body on a D jet 2.0

@JeffBowlsby - you must know the answer to @Stratfink 's question.

i know enough from searching out the very same question in relation to L jet throttle bodies linked to distributors to know that there were 4 different throttle bodies, (theorectically) for the 74 and 75 L jets according to the PET. but those part numbers do not come up as stamps on the throttle bodies. they all just have the same number sequence cast in but not the variant letters that come after the 9 digit part number.

and i've seen the same thing goes for the D jet 2.0 throttle bodies.

they D jets have the same throttle body as far as i can tell for 73 and 74 if you look at the PET. but there are two different throttle bodies for 75 on. one for calif and one for 49 states. i suspect its to do with how you hook up the vac hoses from the distributor.
the question that @Stratfink is asking. is he not?

i don't know about D jets.

but if the same question was asked of me about L jets this would be my answer.
all the L jets can be turned into any of the variants by simply plugging or unplugging the hoses, but you do need to have both ports on the throttle body.
and they all had the retard hose from the distributor hooked up to the throttle body.
it was the advance hose that was either plugged in or not plugged in.

in the case of L jets, if someone said which was the best i would not hestitate to say the 74 49 state. with the vac hoses all hooked up.

why.
because the 74s ran the same ECU. all they did was unplug the hose on the californian cars to make them run at cruise retarded slightly and run hotter, purely for emissions.
it was a dumb as that.

D jet. i don't know about. but i would suspect it was similar?
but i could be way wrong because i really don't know much about D jet.