Almost no HP will be gained. Maybe 50lbs tq, but it will help turbo spool-up by about 200RPM, and frop EGT's about 200*F.
The EGT reduction will allow you to stay in it longer before the EGT's get too high, and the 200RPM earlier spool-up will bring the power on sooner, and decrease smoke.
I did a Cam and Head at the same time and it helped tons! I can run 50Lbs boost with my twins, WOT with the Water temp slowly climbing, and EGT's staying at 1,275.
That's O. D. , 2,200RPM, pulling a good hill with 19K in tow. Takes about 4-5 minutes of 40PSI+ to get the water temp from 190 to 225*, then the truck de-powers and goes into limp mode to prevent overheat, still runs 30PSI.
I would do it if you are going to spend some money anyway. I have a PDR head, and PDR cam, but I've heard the Helix's might be better. Don_M is a great guy, and I would have bought my cam from him, but when I did mine, Piers' was the go to guy.
Merrick