[Nickshu]

You still need it. With the O2 sensor disconnected it pegs the frequency valve at a fixed duty cycle, 50-60% IIRC.

With the O2 disconnected (from what I understand) you do get a more stable idle in the presence of a leaky (vacuum) engine, but you are robbed of WOT performance/output.

Psalt is the expert here, I learned from him here on the forum, I used to have mine disconnected until I truly understood how the system works, now I have it reconnected and dialed in properly. Porsche made many modifications to this system to optomize performance over the standard Lambda K-jetronic that was installed on VW's and Audis of the day. It was not simply a K-jetronic with the Lambda as an add on, it was much more integrated into the system than most people think. This includes the addition of a throttle position sensor that sends a signal to the Lambda brain to offer a richer mixture at certain throttle positions for higher performance at upper RPM's above the level which emissions requirements tested at that time.