Oil pressure gauge is handy cos it should identify low pressure and a worn engine. You can get a different pressure switch which illuminates the low pressure warning light on the dash at a higher pressure. The idea is it alerts u so you have enough time to switch the engine off and save it. Oil temp is good as you should not thrash it when too low and the pressure is too high. Similarly when the temp gets too high the pressure drops so if it goes above 120 C I would slow down. Turbo cooler is like a radiator for the turbo as S2 turbos are water fed for cooling. I have one fitted but not sure it makes that much difference.