1227747 DFCO not working?

Performance wise this engine is running like a dream. I’ve been trying to do some fine tuning to eliminate one minor annoyance. During decel (using the engine for braking) I get a popping out the exhaust right about between 20 and 30 Kpa manifold pressure. Above or below that I get nothing and only when passing through that range. I’ve been trying everything I can think of and it seems like DFCO just isn’t working because there never seems to be a difference no matter what I try. I’ve been running open loop because it seems rock stable that way. Just touching the throttle slightly (to get the manifold pressure out of that range) stops it. Tried so far;
OL AFR vs MAP up and down in that manifold pressure range
'OL decel AFR option' on and off
running OL and CL
OL decel enable RPM at 6350 (stock)
OL decel enable temp 50c
DFCO enable-disable RPM up and down
DFCO MAP enable 13, disable 34Kpa
DFCO pulse width 3.4msec down to 0.0msec
DFCO pulse width delay 400msec
I’m using Tunercat $42

What am I missing/doing wrong here? From what I am researching a VSS is necessary for this function to work and my setup doesn't have one. If I add a 'speedo cable' hall effect sensor do I need to add a 2K resistor to it?

Hello! first things first, Apologies. for I know nothing of this, however I need to learn of DFCO and how to tune it. Im going kinda "oldschool" with the 2002 L31, 411 PCM-2156 OS, and a NV3500. The 5 speed is something I will need to tune the 411 to. A 'seg-swap' would be great, if I could find the .bin for the L31 instead of LS 5 speed.