Just did a long trip across to Broome from Brisbane via Plenty Hwy and Tanami Desert. Somewhere along the way my Patrol has started blowing black smoke when under load. I was towing a camper trailer of 1 tonne and had possibly another half tonne in the car. I have had it to my mechanic a few times and he can't seem to nail the problem. He did find an issue with two short hoses in the turbo area that were cracked and worn so they were replaced and the problem did stop for a short while but has returned. I am a novice when it comes to mechanical problems so any advice I can get I would gladly appreciate.