I have a problem with my new used 300TD. After intial acceleration to 40 mph I look forward to the turbo to get me to the 60 mph to 80 mph. I used to have a smooth transition. Now when I give it the gas it needs to get to 60 mph I get a loss of power and big black smoke clouds out of the exhaust. I am at a loss as to what this could be. This is the first Diesel I have owned and need some pointers on it general care as well.