Stumped

Lost exhaust brake function on my tow truck. First reaction was bad actuator at 217k. Replaced the factory turbo with a 60/60 tow boss from stainless. Sweet new parts!. Great on the go, still missing the whoa. Swapped the exhaust back pressure sensor, now the brake will chug, engage, back off, engage, back off, then it's gone, less than 20HP effort. Actuator clearly works, but something else is not getting the signal across. What else drives that function? Need the brake, it's a ton truck that works for it's keep & routinely pulls way out of factory spec as seen below.

Here's what's going on.

Did the actuator on the new turbo come learned?

With what's going on, I am wondering if the turbo control module is done. It's located behind the oil filter on the block. There should be a code or two if the turbo module is going out. Comes down to whether or not the tuner still has them enabled.