converting a 1 wire o2 to a 4 wire heated o2 ?
 

Is this do able?

I think I saw a device for sale that takes a wide-band O2 sensor, and then (based upon how you programmed the device) emulates a narrow-band O2 sensor (and I think one or two other car sensors as well).

The idea being, that this device could directly plug into a stock car, but allow you to tweak the fuel map (in the device itself), and then let the device fake the (narrow band) O2 signals going to the stock car ECU (to give you the fuel tweaking you desired). However, I can't remember right now where I saw the thing for sale (and, naturally YMMV as I haven't actually tried the device myself)...

Well, 4 wire, directly, not really (that's a wideband O2). The issue is that the computer isn't designed to work with a 5 volt variance and doesn't know what to do with those inputs. AEM has an add-on wideband, but I dont' see the advantage of using the narrowband output from that compared to a standard narrowband o2 sensor.

Depending on the vehicle, it is entirely possible to use a 3 wire heated o2 sensor. Harness pigtails may not match, and you'll have to do some homework on how your particular one functions.

Find a device that actuates or sends a signal when the ECU goes into closed loop, use that to cut the heater circuit (Which you wire yourself). The ground can be taken to an ECU sensor ground or the battery ground, the signal goes to the single wire you have now.

However..... if the ECU completely ignores the O2 until it goes into closed loop, then you'll probably gain no advantage whatsoever. Heated O2s are used so that ECU can go into a halfassed closed loop mode soon after startup, and not just run rich until the engine is warm. If your ECU isn't looking to do that, then the few minutes for the engine to warm enough for the ECU to read the coolant temp sensor as hot enough to go into closed loop will probably have got the O2 hot enough.