This is my first post on here and I couldn’t figure out this problem I’m having. So I have a rough idle on my 1990 civic hatchback and have tried a lot to fix it. But I still think it’s either a missing sensor or a vacuum leak. I bought it a few months ago and it had an after market intake on it and there’s a spot where a sensor or vacuum line looks like it would go there. Does anyone have any ideas on what it could be?

 

Cover the holes in that spot with your fingers. Does the engine now idle smoothly?