Strange Throttle on Deceleration

[2005300c]

I've got a 2015 Challenger R/T that's running a Diablo 91 octane tune that my CMR raised the rev limiter on, along with a CMR TCM tune. The issue I'm having relates to how the engine behaves when decelerating.

As an example, if I have the car in sport mode and I'm driving down my neighborhood road at say 25 mph and I let off the gas, the car will decelerate like you would expect. However, after getting to roughly 18-20 mph, the deceleration stops and the car begins to accelerate. And I don't mean it stops slowing down, it picks up speed, even if I'm going uphill. It'll continue to accelerate until about 25-30 mph, then begin deceleration again and the whole slow down/speed up loop starts again.

If I'm not in sport mode a secondary symptom of this is the transmission shudders on deceleration when dropping from 5th to 4th, and again from 4th to 3rd.

I tried reducing throttle boost by -10%, but it really had no effect. If I run my CMR tune, I get the same thing. The only way to eliminate the issue is to run the stock tune.

I've attached the last written tune files - anyone have a suggestion?