Welcome. You found the right place. Tell us how all you want to use the rig and how many millions of dollars to throw at it, and we can walk you through building it for the race to the moon. Haha
“Low clicks no power” Are you saying it isn’t starting and all you here is clicking sound?
Disconnect battery cables, Check both batteries are fully charged, clean the contact area of the cables and pay special attention to the stupid disk between the two cables. (Long term loose the side post for top post batteries imo.). After that you might need to drop the starter, clean the battery cable to it, and bench test the starter. If ya dont know how, let us know we can walk you through diy or take to local auto parts store for testing.
If starter is bad- the Powermaster 9052 is the best starter for this hands down. The battery cables could be toast also, corroded on the inside. When time to replace them, upgrade them to a better cable for better starting and longer battery life.
My read of "Low clicks now power" is low mileage (clicks) and OE (no) power.
There are still some tricks to wake-up the 6.5 a bit, but watch out as some tricks are more hype than actual benefit. Getting up to ~400 ft / lbs is reachable, but past that and the motor needs more supporting mods and durability tends to go down.
The best thing to do is list the goals for this 6.5 as there are different upgrade paths depending on the goal.
At a minimum, the K47 airbox and aftermarket exhaust (3" downpipe and 4" back) are beneficial for any upgrade path.
OE turbo is holding back the motor, but a choice of aftermaket replacement is dependent on the goals question.
OE injectors are actually OK as long as they are healthy. While there is internet lore of marine injectors offering a bit more power within some RPM ranges, my experience is that they only smoke more and make the motor less responsive to throttle inputs.