95 850 - warm engine stalls and wobbly minimum

[dartagnam]

Hi all, I am a proud owner of a (rare here in Italy) 1995 854 GLT, NA engine.

It's been some time I've been experiencing issues when the engine is warm. I'm going to describe contexts and symptoms:

I drive the brick approx once a week, mostly highway use. Car has 86k miles.

Problem:
1 - When the engine is warm the car stalls when I stop (e.g. at the toll both or intersection). i fire it up right away and the idles oscillates between 300-1200 rpms, as if the ECU keeps it up. From now on, every time I stop at an upcoming intersection I have to keep the engine awake by keeping the pedal pressed a bit.
Cold engine: nothing.
2 - If I hard tap on the pedal I often hear like a puff noise, like if the car has a turbo valve, as if air is coming out from something.
3 - Let's suppose I'm on the highway at 2500 rpms; I accelerate at full throttle to 5000, but the progression is not so regular, the engine has some hesitations along the way.

What I've done so far:
Cleaned the IAC with steel cleaner. Cleaned the throttle body. The MAF seems to be working as I unplugged it when cold and the engine tended to turn off.

My mechanic (sadly too far from me, I bought the car from him but relocated in the meantime) suspects there's some air infiltration and advised to check the vacuum lines for some leak. Now I've done so but seemed not to find anything. I attached a pic of the vacuum tree.

Now I've checked multiple other topics in the forum (viewtopic.php?t=91482&start=10 , this viewtopic.php?t=39224 and viewtopic.php?t=16152 for instance), seems so common but with many little variations in the car's behavior. Seems to be quite infamous.

What do you think about it? Would you advise to check anything else?

[Sveedy]

Maybe check the engine temperature sensor and its connection located just below the thermostat housing. These cars act weird when that sensor starts to go.
And Welcome !

[volvolugnut]

I still suspect a vacuum leak. Spray all vacuum hoses with carb claener and listen for RPM increase. Try a smoke test. Your hoses look a little aged to me.
volvolugnut

[dartagnam]

Sorry for the silly question, you mean right on the surface of the hoses or inside?

[scot850]

Spray around the hoses from the outside, and along the joins of the manifolds to the engine. If there is a vacuum leak it will suck the fluid in and the RPM will increase.

Neil.

[volvolugnut]

Spray around the hoses from the outside, and along the joins of the manifolds to the engine. If there is a vacuum leak it will suck the fluid in and the RPM will increase.

Neil.

Yes, that is what I meant.
volvolugnut

[scot850]

I knew this is what you meant, just added for clarity. OP was not clear.

Neil.

[dartagnam]

Thank you very much everyone for the clear explanation, I will try that and let you know.