When I decel my O2 readings fall to 0.000 and it happens randomly at idle and part throttle. Is this normal, or is that why my engine always runs choppy and no amount of tuning helps??

Decel, no fuel no O2, that is normal.

The idle/part throttle is normal, for a cold O2.

Mine does that. Install a heated O2 and things will calm down. O2 has to be over 600 F to work right, a cold O2 will send a lean reading (low voltage) to ECM and car will run rich. Your city mpg should be a lot worse than your trip mpg.

I have a Stock OEM shorty header and no cat.

Thanks. I have Flowtech headers. The sensor is really close to where all the tubes come together, but I guess that thin steel makes it cool really quick. I'm not sure how to wire a heated O2, but maybe someone here will help me out if I haven't pi**ed to many people off yet.

Do not worry about it. Most people here are to learn and help.

This a generic NBO link (for Jag)
http://jaguar.professional.org/O2/index.php

Three wire harness is a good solution for heated sensor. Use AC-Delco AFS-74 NBO and PT643 pigtail or Dorman 85393 connector or equivalent. It is very easy to retrofit three wire NBO. On Delco units usually purple wire runs to ECM. You'll have to make switched heater circuit - a simple relay activated of a fuel pump circuit or other ignition hot circuit will do the trick.
http://www.thirdgen.org/techboard/di...sor-165-a.html (Heated O2 Sensor and 165 ECM)

//RF

Not me, not yet, not likely.