If I'm gonna run a heated O2 sensor, what do I change inthe PROM? I'm using a 7747 ECM.

 

Don't really need to do much. Maybe change the warm closed loop timer to a lower number. So if you restart the car and the coolant temp is already high enough for closed loop, the car will go into closed loop faster than before.
The advantage of the heated o2 sensor seems to be it's accuracy. It's not as easily influenced by different exhaust systems which could effect EGT (exhaust gas temp).
I think if you did a search for heated o2 sensor it'll turn up a bunch of good topics that answer the question better.

 

My van originally had a heated O2 sensor in the Y-pipe. When I would start it cold, it would idle like **** after a minute or two. It would rev up and down and trigger the stall saver. So I welded a bung in the drivers side "collecter" right below the manifold and spliced a non-heated O2 sensor into the harness and it works great (the heated one is just there as a plug now).

I would like to use the one in the Y-pipe but every time I switch back to it the thing doesn't want to idle.

I was thinking maybe the cold closed loop time was set too high. But I just went thru and looked at some other bins and the cold closed loop timer isn't much different than mine.

 

Did you try replacing that heated sensor with a new one? I see no reason why a heated sensor would cause any sort of trouble unless it was defective.

 

It worked fine with the original V6 and ECM. Then I switched to the 7747 ECM and it acted funny.