I was able to put down 486 RWHP at 989 LbFt of Torque with Single Stock CP3, Stock Injectors, Stock Turbo, FASS Lift Pump, see list below.
The largest improvement was whith a "Quality" EFI Live tune from ATP, Adrenaline Truck Performance, Idaho Rob Coddens. Tuner recommended by Guy Tripp at SoCal Diesel.
I find the best way to develop the HP/Torque you really need is to start with the basics and then build on them. Ask the very knowledgeable people posting on this website and ask lots of questions. It will save a lot of time, money and frustration in the end.
I hope this helps.