Dual Cp3's can cause engine failure to occur sooner. Injectors are a good idea, get a 40% over nozzle and you can tune the engnine safer and achieve higher hp.

injectors help out a lot with cutting down pulse-width and timing, if you do the math and figure out how long injectors are open for with some of the big tunes people are running its some scary stuff.

one cp3 can generate enough fuel to feed that kind of power, the problem is air. bigger injector are good but they arent needed if you can cram some good air and efi tuning helps. a lbz/lmm cp3 is a good upgrade from stock thats cost effective for your goal

dual cp3s will only make you want to tune it more aggressively and you will start to break stuff.

The head studs, its kinda of a no/nogo thing, the head gaskets on the 01's arent as good as the 02 and up dmaxes, but they are still enough to do work. theres some mixed ideas on the studs though, some people like to do them because they dont want to have to tear down the heads from stretching the bolts from adding more power, while others leave it alone and not worry about it since the heads going can usually indicate your on the verge on bending a rod (in some cases).

But Me, i studded mine. Theres been a number of guys who have bent rods without ruining the head gaskets also.

so i think i will defintly run head studs. and the resone i may still run dual cp3's is cuz eventully id like to build the engine up more.

if your going to run the head studs, i recommend doing it right before yuo add the dual cp3's

but after swapping a lbz/lmm cp3 in there yo will find there is not a need for that untill a long way ahead