96 Silverado 4.3 NV3500 swapping 2005 5.3 (L33) issues

[Pancho96]

Having an issue with a 5.3 swap into my OBS. Truck is a 96 silverado it is originally a v6 5 speed. I am leaving the NV3500 it came with. Truck will start fine and idle good but when you rev it up it starts to surge. RPMS will go from about 2000 down to 800 when giving it throttle. Idle is fine it?ll idle around 650ish. Did smoke test for vacuum leaks and nothing came up. Fuel pressure on the rail is about 55psi on idle and when under load. Also plugs cables and O2 sensors were all replaced and nothing changed. Noticed bank 1 O2 sensor was reading almost at 0 mv so thought maybe that was the issue so went ahead and replaced both but that wasnt the problem. MAF sensor has been replaced with a known working one and still nothing. I have turned off VATS. Transmission type has been changed to manual in the drop down menu and PRNDL has been turned off. Also any CEL lights not needed have been turned off. Also truck has open headers right now havent got exhaust done on it yet not sure if that could be causing this issue. Im stuck and cant figure the issue out im not too familar with the actual tuning aspect of hp tuners im a beginner to this part of cars. Not sure if this is an issue that can get professionally tuned out or am i just forgetting a certain parameter that needs to be changed for this too work? Any help will be appreciated.

[2xLS1]

You can not run a closed loop system with O2 feedback with open headers. If you MUST run it that way then unplug the O2s so it stays in open loop. And if you are going to try and run a MT vehicle with an auto trans OS then you must disable Torque Management in both the engine and transmission segments. Setting the trans type to manual does not make it a MT OS. Starting with a MT OS would be preferred.

[Pancho96]

Will disabling TM in both places fix my issue? In the transmission option is that disabling abuse mode? Im new to this stuff i cant seem to find how to disable TM in the engine option. Thank you.

[RDF1]

Posting your tune will help alot.
Engine Tab - Torque Management Tab - General tab