Driving it off the cliff

[Stl-986]

As a test I went ahead and used the hand pump and pumped it up to 20hg before heading out to dinner. Came back 2 hours later and it has held at 20hg. This is with it just teed into the vac lines and the engine off.

[blue62]

Originally Posted by Stl-986

As a test I went ahead and used the hand pump and pumped it up to 20hg before heading out to dinner. Came back 2 hours later and it has held at 20hg. This is with it just teed into the vac lines and the engine off.

Have you tried disconnecting the vacuum hose for the SAI from the intake then plug the hole in the intake.
Then see if you still get misfires?

Your test is a good test.
But there is an electrical vacuum switching valve in the SAI system.
Engine off it is not being activated perhaps it is faulty and sticks open with engine running.
Just spit balling.

Disconnecting the vacuum source to the SAI would be a good test.
Simple also.