Vacuum leak after Intake gasket replaced

Car: 2001 Chevy Lumina
Problem: Vacuum leak, poor idle

Hey there! This problem has been the bane of my existence for the past month or so and I’d greatly appreciate any input. It all started when I had a badly leaking intake manifold gasket about a month ago which left me on the side of the road (no amount of water would be enough for this leak). I got the car towed to my house and tried to find a mechanic to fix it but none in my area even wanted the job. I did get 1 guy that said he’d look at it but for some reason he just wanted to string me along rather than just telling me he can’t do it, he ended up wasting 2 weeks of my time and only gives me excuses when I call him. I suppose I could take it to the dealership but they would likely charge as much as the car is worth.

After a few weeks I got fed up and watched some youtube videos and decided to tackle the job myself (I’ve done smaller jobs before and all went well). I was able to take everything off, replace the gasket, and put everything back together. I actually did fix the coolant leak but now the engine is running rough, has a high idle (2000 rpm) and is making a high pitched noise that’s especially bad in idle. I don’t have fancy equipment but I do have a basic scanner- the codes are P101 (mass airflow sensor) and P300 (random misfires). I suspect there is a vacuum leak somewhere but everywhere I look I’m noticing problems- I noticed my spark plug wires were damaged, some wiring was damaged, and some vacuum lines were damaged. I went through and replaced everything I noticed (I had no idea taking everything apart would cause so much damage) but I suspect there may be other issues.

In an effort to find the leak I sprayed carb cleaner around. The only place I noticed a difference was near the fuel injectors. I am willing to take the upper intake off to check them but I’d like to know if there’s anything else I should check while I have the top off. I suspect I may have to do the entire job again so any help to avoid that would be greatly appreciated.
Thanks!

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