It sounds like you could have a problem, But with out knowing everything about the truck and seeing the smoke it will be hard to know for sure.
A dirty air filter can cause more black smoke, but at only 5200 miles, I wouldn't think that to be the problem. If the smoke is black or very dark, it is not a fuel leak. so the injectors should be ok. It sounds like a timing problem is possible.
A dirty air filter can cause more black smoke, but at only 5200 miles, I wouldn't think that to be the problem. If the smoke is black or very dark, it is not a fuel leak. so the injectors should be ok. It sounds like a timing problem is possible.