I am running a 700R4 behind an LQ4 and I have the park/neutral pcm input wired to see ground when in p/n. This works fine but it does have a delay.
I can drop it in gear and it idles and runs just fine, but once the delay has passed and the ECM sees the change (well after its already been in gear) It will stumble and make crazy idle speed changes. I have set the p/n enrichment to 0 and both idle speeds for p/n and in gear are the same. The timing tables are also the same for idle p/n and idle in gear. Oh I have also messed around with some friction air flow settings to see if that helped, it really didn't.

Is there something else I am missing here that could be causing this?

One thing I did notice was that when the pcm detects the change it locks out the adaptive spark and holds solid at 22.5 degrees. After a few seconds the adaptive spark comes back.