Heres the factory wiring fo a 87 Turbo

 

Are you sure there are electrical connection inside that "shunt"? That diagram shows no connections inside the shunt. It could only be a cover for the connector.
It also makes no sense to short the O2 sensor input to ground since this situation (no O2 sensor) is arraged for in the DME hardware.

 

Use the impedance adapter to force open loop operation. Otherwise the DME will still attempt to go closed loop. The processor only sees a binary value from the O2 input: rich or lean. It will interpret the .5V one way or the other and act accordingly.

Forcing the O2 input to ground for non-cat cars will protect the O2 input circuit.

 

It is a plug that connects in where the O2 sensor would and has an external wire loop. I will check which pins next time I see one and take a picture.
Tony

 

TT, When I disconnect the O2 sensor the AFR is very stable on the meter, but typically lights up 2-3 of the 20 LED’s.
This feature, btw, enables me to communicate to Danno where to add and/or remove fuel for custom chips for high boost with water injection. Using my previous chips in my “new” back 951 gives surprisingly different results (less fuel needed at idle and more at high boost). My guess is that the change in leak-down and better exhaust are the main reasons.

Mark944turbo, I got another 951 (mentioned in “New addition to the family” thread) and yes I continue to pursue reliable 25psi boost on a standard K26-6. This time more cautiously, by monitoring the EGT (and other parameters), being more respectful of missing combustion and adjusting the water flow accordingly.