Someone has not been servicing there engine...
The condition of that water is terrible and looks like a completely blocked oil way..
Did the oil and water contaminate each other or something?
Was there no service history to accompany the car?
Some people are blind to the needs of a car...
Also some people see the service as a crazy expensive payment, when in fact if they just can't afford it they could simply change the oil and filters personally for less than £75... and an hour of their time.
I have srevived my mazda (basic oil and filters ) twice myself and once at garage to get service history proof.
Best to keep these things in good condition internally
Is that the oil diaphragm unit where the black gunge is?
They have a heater element in them - mine failed a few years back and was throwing up engine lights due to the fuse going. The gunge isn't related to that kind of failure is it? thinking if the heater went open circuit you'd not get the fuse blowing like mine did.
Any update?
After having all that done i would 100% get it mapped and the intercooler done. Especially if Gary is offering good labour rates. It's always recommended on the ST forums to remap 2.5T to wake it up so I'm sure it will give the car a new lease of life and feel more fun to drive for years to come.
Was going to get my ST remapped but after losing all my coolant last month due to a split pipe and it overheating I'm not sure I trust it now. as I've been told it's probably stressed the head gasket.