Just to post an update, I installed my WBO2 to look at the logs to see where my issue may be. On a couple hour highway cruise I stayed right around stoich, so that made me even more confused as to what the issue could be. The next day I started my car up cold and noticed that it went right up to stoich (kinda a giveaway as to the problem). I changed my thermostat, and now at warm up i'm in the mid 13's. I have yet to "verify" my mpg's are fixed, but idle is smoother and I think the issue is that the thermostat was not working "sometimes" which would throw my car in warm up mode while cruising. It's always the intermittent problems which give the most trouble....

To my dismay, I have to revive this thread. Once again, I am getting low gas mileage, but worse yet, I am getting very hesitant starts. The car turns over strong for 2-4 seconds, finally catches, then is followed up with misfiring for another second or two. Once the car is idling, it is relatively smooth (it's still a 4 cyl). I pulled my plugs today and found spark plug in cyl #2 was slightly white whereas all the others are normal. I compression tested and got right around 195 on all 4 cylinders. With the key on (not started) I can hear a high electrical humm near the injectors, but I am not sure if that is normal. I had an issue where I wasn't getting spark a few days ago, and after plugging back in and out my CPS that issue was gone. My thoughts:

Injector(s): If 1 injector was bad enough to cause a bad start for the hole engine, wouldn't my idle be rough? Also, looking at my WBo2, I am idling/cruising around stoich, and at WOT it'll go down to 12.5ish.

CPS: If my Cps was going bad, wouldn't I be getting a bad idle? Also does not explain cyl2 lean condition.

ECU: If the stock ECU was bad (this car was kept in a garage most of its life) I feel like there would be other problems. This is so rare I cannot imaging that being the issue.

Ignition Coils: This is the second brand new OEM Mazda ignition pack....I really doubt 2 would just "fail." I gapped down to .040 and no difference.

I am totally out of ideas....I feel like I have tried everything and nothing will make sense of the issue. :vash: