The MS6 uses 2 oxygen sensors: One right after the turbo, which is a wideband, which I recommend you DO NOT tap into at all. There is a second O2 sensor, located after the first cat, but before the second cat. This is a normal narrow-band O2 sensor, that if you had to tap into, I would recommend this one.
Just buy an aftermarket wideband 02 sensor and use the 0-5VDC output for the turbo timer. From the sounds of it, you plan on doing serious modding, and the A/F ratio gauge should be your 3rd modificaton after a boost gauge, and intake.
Granted, I never installed a turbo timer, but what does the oxygen sensor wire have to do with a turbo timer?
Fill me in ...