The oil pressure gauge has been successfully installed with no hassle whatsoever. Guiding the wiring through the factory door harness was a bit tricky but nothing too annoying.
The ventilation hole for the door had to be blocked out, was quite a simple job too:
And then the crazy business with oil cooler installation.
The oil cooler install was simple, I only have to note that you need to remove the crash bar to install it, otherwise you can't drill a hole to hold the oil cooler in place.
Also, don't forget to fill the oil cooler with oil all the way up before installing it - you don't want that engine to starve for oil once the thermostat opens and sends oil down the hoses to the oil cooler.
Routing the hoses wasn't a problem, I found out the nicest way to route it is beneath the washer fluid, but you need to cut a small hole (7x7cm) to route the hoses through it:
The worst headaches caused were by the pressure sensor. I got the adapter necessary:
but there was just no room for everything. I had to add another small extender, because I would either have to get rid of the standard pressure sensor, or the anti-roll-bar or something else. It was a headache, but i managed.
Finally, put back everything together, looks unsuspecting but obvious to the trained eye.
I just turned on the car once, to check for leaks, all is GOOD, however I couldn't run it up to working temperature in the garage, so that the thermostat would open and I could actually test the cooler itself, but that part will be tested in spring, once the car is out of garage.
This turn-on pressure read as ~7-8 BAR, then slowly dropping to about 5 BAR, when I already turned off the car as you can't really run it in the garage....
So yeah. One crucial upgrade done. Next part - upgrading brake lines, change of brake fluid and installing some brake cooling ducts.