What sort of power issues? If you lack the power you previously had, then the answer is almost sure either the fuel filter(s) or maybe a clogged fuel lift pump intake.
If you never had enough power and want more hp, then you need more fundamental changes. Start with air flow (which includes exhaust) per Mike Cantor's advice. Odds are your present injectors can deliver all the fuel your engine can ever use.
There are power improvement kits available for some engines. Check with websites such as Redlands RV Performance
, Banks Power, Diesel Performance
, Xtreme Diesel
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL