If you never drive it up on the highway you won't need it. They really open up and start to work on the highway, thats when most old ones blow a hose to. I think on the 603 the T stat for the cooler fully opens when the oil is 90C. You notice this because you lose about 1/4 bar of oil pressure when it does.
If you want to know how hot your oil gets just drive the car on the highway for a bit, and shoot the oil cooler intake line with a inferred thermometer.
Like I said above, if the car is a beater and you don't fell like spending $100 on new lines by pass it. If the car is not a beater I don't get what you are trying to gain. I don't understand why anyone would remove a perfectly fine oil cooler?
