GM-GMC: 7.4L Low power and Overheating, intake leaks, vacuum gauge

Question
I have a 1996 Chevrolet 3500 HD the entire cooling system has been replaced with new parts and I still seam to have a problem with the temperature running about 220. It dosen't seem to have the power that it should have for such a large displacement. The truck has a little over 50,000 miles on it and has been expertly maintained its whole life. This has the mechanic who has always serviced it and myself puzzled. I will be grateful for any suggestions.  

Answer
The operating temperature is too high and will, if it has not already, damage the engine.

A vacuum gauge is still one of the best diagnostic tools out there.  It can tell a mechanic about the condition of the valves, valve timing, and exhaust system as well as detect intake leaks.

In fact, one of the things I would check for is a restriction in the exhaust, either in the catalytic converter and/or muffler.