Disco 2 Where's this vacuum leak smoke coming from? 4L V8 with rough idle

I have rough idle in a 4L V8 Discovery 2 I bought a few months ago and I've changed a lot of parts (see post here with symptoms and list of all work done).

I made a DIY smoke machine and have smoke coming out from somewhere deep in the engine. But I can't see where exactly:



Questions:

1. What part(s) are easy to remove to get a better look?

2. Should I connect the smoke machine to somewhere else as well to check? Currently fed in from where the MAF would be.

3. It runs lean. Is it safe to drive the car while I figure out the source/fix? Or can I damage injectors, O2s, cats, etc.?

tl;dr
- Coming from deep somewhere near the injector area? Gasket? There's also a few smaller hints here and there in my videos.
- None coming from the oil cap when removed.
- A bit coming from brake booster hose. But not much?

Birds eye view from top down:​

Here you can see it also comes out a bit up top nearer to the windshield.

Air leak from booster cable:​

Taking off the oil cap:​

Folks are suggesting it could be:
1) upper intake manifold gasket (was recently replaced by a mechanic) misaligned
2) lower intake manifold gasket (also called the valley gasket?)
3) fuel injector o-rings

Any idea what parts I can remove to get a better look to confirm without doing a big job? Just so I know which parts to order/buy.

Edit/update: Solved!

I replaced valley gasket and fuel injector orings

More details on the other thread: https://www.landyzone.co.uk/land-ro...tried-maf-o2-sparks-leads.392992/post-5732844