1986 2M4
How much suction should be on the brake booster line when it's disconnected, should the RPM's change when its disconnected?
I was using seafoam and use that line to feed it and there was some suction but not like I thought, when I dumped the line right in for the last drop to stall it, it never stalled.
On all my other cars that I drove when disconnecting the PCV valve there was a considerable suction, etc. On the fiero when I disconnect it, there is not a lot.

Where does the brake booster line hook up to on the engine?
Any thoughts

Booster Vac Line gets Full Manifold Vacuum. If the engine even runs should have very high idle and maybe setting DTC for IAC problems.

Depending on year of Fiero... 3/8" 84-86, 1/2" 87-88 hoses and hose fitting.

84-86 uses filter in engine bay. No flow then check for blocked filter.
See my Cave, Brake Service

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)