FNG with questions and advice needed

Howdy all,
FNG here with a 99.5 super duty 7.3psd and had a few questions and need some advice;
First, my super duty fires right up everytime and runs up/down the road fine, no lights at all on the dash (they all work), BUT,
-My 7.3 seems to have a VERY SLIGHT rough idle, not bad or even really noticeable to most, but I'm wondering if its a precursor to something I'll need to adjust/replace?
-Also, my 7.3 seems really down on power, theres just not much there and I'm wondering if that's another precursor to indicate maintenance that's needed?
(I've owned a NA 7.3idi and turbocharged 6.9idi as well as currently using a cummins for work so I don't expect "race car performance" but do expect SOME "get-up-and-go" when I hit the pedal.)
Lastly,
I'm planning some perf upgrades to my 7.3 and wondering which is the biggest "bang-for-the-buck" modification?
I was looking at a tuner, exhaust, cold air intake, compressor wheel, etc. Again I'm not looking for "race car" perf, just an increase.
Thanks for any info and input guys!