If you have a scanner that can only check for codes than this may not help , but is still a starting point. If you think the turbo growls to much when shut off then you should check the turbine shaft for excessive play , check this by removing the air intake tubes to the turbo inlet and then move the turbine by hand there should be little to no play up / down / left / right . If that is ok then a scanner will be required. Black smoke can be caused by so many different items on this truck that telling you just one item to replace based on a symptom would not be fair to you or very accurate. Common components that cause black smoke and a lack of power are, turbo stuck, egr valve stuck, low fuel pressure, restricted exhaust, low compression,blown intercooler, exhaust leaks. All these require a advanced scan tool to diagnose. You could also remove the egr valve and inspect for carbon holding the valve open , and clean as required. The egr valve is located just to the right of the oil filter . I would also replace the fuel filters if not done in the last 15,000 miles.