aggressively weird idle having to do with vacuum lines

[RedZed]

Hello everybody, I have a Excalibur Cobra with a 1995 mustang 5.0 in it. when replacing my vacuum lines last week due to surging while driving I noticed the vacuum line under the intake plenum was unplugged. (has a 1993 cobra intake.)

I plugged in the vacuum line to the manifold and the car runs terrible with idle bouncing between 600 and 1000 RPMS. when I unplug the vacuum line the engine idles fine. the problem is the vehicle is pulling unmetered/unfiltered air from the underside of the manifold.

when looking up the vacuum line diagram for a 1995 mustang 5.0 I see a solid vacuum line running to the intake manifold from the charcoal canister through the evap vent solenoid. I replaced the solenoid thinking that its not opening but its still idling funny.

has anybody just put a breather filter on the vacuum line connected to the intake manifold and called it a day? I was trying to "do it right" but now I am thinking of just deleting the charcoal canister and evap solenoid all together so it runs right...It no longer needs emissions in WI.

also as an aside, the vacuum line for the interior vent controls was hooked up to this as well which I dont think is right...does anybody have a diagram of this?

Thank you for taking a look!