I would suggest first things first...
They are two very good fuel system cleaners out there - BG 44K and Techron - and either can be used to clean up the system a bit, applies to gas or diesels, great for both !
Best done immeditely before a oil change, run the tank down below 1/4, add the fuel system cleaner, top off to a full tank.... run thru that tank and a second tank...
For really bad fouling, I suggest going thru 2 applications of the same product, total 4 tanks of fuel - then go for a oil change (since some of the solvent and byporucts get into the oil from blowback)...
You investment will be total under $20 (make sure to use the large bottle of Techron, not the small bottle) and you won't have touched a wrench.
If that doesn't bring your perfomance up, then you could consider a "purge" your choice at a reasonable priced shop or DIY.
Note, routine use of either BG 44K or Techron, one bottle and (2) tankfuls before each oil change can really-really help long term reliability and performance.
On diesels, it is not uncommon for a owner, who has not regularly run a fuel system cleaner, to get past the point of no return and rebuilt injectors