Audi A3 - Slight Coolant Leak

[am1994]

Hello everyone, few months after I bought my Audi A3 1.8L, I noticed a small coolant leak and since then I've had to top it up with around 100ml of coolant every month or so.
Yesterday, I decided to take the car to the mechanic  to see if he can spot where the leak is coming from.
Initially, he thought it was the radiator, but after the put the car in the ramp and did a coolant pressure test, it appears that the leak is coming from that small black item in the picture and it might be also dripping from near the engine.
I haven't noticed any coolant smell or white smoke from the exhaust to suggest head gasket leak.
Does anyone know what that black item might be? Thermostat/water pump didn't seem to have any coolant residue
The mechanic told me that if I want to do a further check on the coolant leak, the intake manifold will have to be removed. That would alone cost me around 300-400 GBP and I don't think is worth going that route for a 15 year old car.

Edited 16 hours ago by am1994