I have a Tacoma and, when starting it in the mornings, the oil pressure raises to 70 lbs. But when the temperature reaches its normal range, the pressure drops to 10 lbs. When accelerating it to 5000 rpm, pressure only raises until 30lbs. I am a mechanic myself and have already checked everything, bearings, rods and even camshaft and they are alright. I've changed the oil pump but still cannot find where the oil pressure might be escaping. Does someone know which is the secret with this van's engine?