i have a 2003 3500 cummins i have a cold air 4 inch back and a smarty and a rebilt trans and still not fast for me what eles can i do and stack and i was told to put a fass pump on my truck too

 

get that pump and some decent injectors and your smarty will really come to life.

 

what size injectors

 

depends on what your plans are for your truck. anything between 50 and 75 hp shouldn't mess up your mpgs too much.

 

What about 150

 

unless you gotta huge single or twins to use all that fuel. your gonna smoke out the universe.

 

No I have stock Turbo but need more low end and what can i stack with my truck and what is stock size

 

dont stack it just throw the money towards building it right instead of what ever you breakbeen there done that its bs stacking it i learnd now money ahead just to build it --------------- head studs turbo twins or single injectors just to start do the lift pump for sure