I never had problems with the oil pressure  :-?

Have you got a constant fuelflow to all engines?

Maybe there could also be a problem with the fuelbalance/fuelmanagement. Check the Fuelpanel. I recommend 25 % IN EACH Tank for short flights / testflights.

And, of course, this old lady eat runways for breakfast xD  ;D - particularly with high GW, there you need 10K Feet Minimum. I've done a start on a 8000 Feet RW with Full Fuelload but very few payload (no wind). It was very close. At the end there are no high obstacles allowed  ;D

Don't forget to activate the brakes while you push up the pressure to 2.0, then release the brakes.