2005 GMC PPE Stage 4 Cold Start and 0-60!

2005 GMC 2500HD Duramax.
I turned up the tuner to stage 4, but I think the transmission is slipping.
In 2wd the truck roasts the tires into 3rd gear, (on 33s mind you) so I will just turn down the tune and keep the transmission alive until we pull the motor this spring to fix a rear main seal.
I've been considering a billet triple disc torque converter, as the truck still has the stock one.
I still can't decide on a stall speed though and would appreciate any advice that could help!
Truck setup:
3" downpipe into 4" to 6" full length exhaust.
30% over injectors
Mahle 16.5:1 reduced compression pistons
Wicked wheel 2 (stock 68mm turbo)
BD Diesel driver side exhaust manifold
Upgraded turbo intake elbow
Airdog 160gph Lift pump
Ported fuel rail fittings.
PPE Xcelerator tuner
PPE Aluminum Deep oil pan
PPE Transmission filter