1993 blazer rough idle.. sort of

Hi I just bought a 93 blazer 4.3 HO W code Blazer. THe thing runs great and only has 61k miles on it. Anyway when at idle the thing idles kind of rough and change RPM's while doing so.(mostly in Park) It also starts a little hard when it has been driven for a while. I'm wondering if I have an EGR valve problem or possibly something else. Engine sounds healthy and runs great and really moves down the road. Now I'm also wondering if it could be an exhaust problem. No sulphur smell or gas smells. THere is carbon in the exhaust pipe.
THanks for the help in advance and hopefully I can get this thing running absolutely perfect.

Have you done anything at all to it? I would start with the following.

Plugs
Wires
Rotor Cap and Button
PCV
Fuel Filter
Check Vacuum Hoses

Getting a muffler tomorrow because it has a hole in it. Had a full tune up before I bought it.

Check the gap on the spark plugs and check the timming.

THanks for the help. The new Flowmaster makes all the difference in the world. THe car runs better and sounds awesome. A problem I still have is that it smokes a little when I fire it up which might explain why it has an idle that is rougher than I would like. I am going to change the oil in the next few days and lube it up real good because who knows when it was done last. What causes carbon to be in the exhaust pipe? I believe that whatever my problem is, that is one of the symptoms. THanks in advance.