Finally decided to replace the irridum Pulstar plugs out after ~80K, last time I looked at them was @15K.20:1!! With my plenum based system, I would get misfires around 17.5:1. My WBO2 sensor is giving me big swing from super rich to super lean it will occilate from the 9s to low 20s and there seems to be no rhyme or reason to it. It will also stick on 21+ for several seconds then it goes off line and flashes 7.4 until I cycle the key. I have another O2 sensor at the shop and may try that and re-calibrate. I've already done several free-air calibrations with this one with no joy.
I'm also wondering if my exhaust has anything to do with it. My O2 sensor is just before it goes into the 911 Banana can. I've been wondering if any back pulsing is giving erroneous readings and causing my wild fluctuations. I still think it's a sensor/controller issue though.
The electrodes on the irridium plugs I had on the 2056cc were gone; and I mean down to the porcelain. I had been running them since first going to MS in 2009. I probably had 80K on that set which was amazing! I had checked them a year or so and they looked fine. I probably put 20K miles on them over the last year before installing the new engine and had planned on running them in the new motor since they had been so nice all that time. I had noticed for the last couple months of driving the 2056cc that it would sometimes knock on full load when the engine was fully warmed-up, so I just backed off the timing a degree or so. When I pulled the motor and went to pull the plugs I was a bit shocked at the condition of the plugs. I'll bet the new gap was around .140". I had originally gapped them at around .035".
I think i got my moneys worth.
Wouldn't pull 19:1 AFR at cruise anymore for some reason, but 17:1 was fine.
Running LS2 coils. Still ran great, last tank was 30 MPG.
A couple electrodes do manage to just peek above the insulator.
I'm putting the old JAW wideband back in and am going back to 22:1 at cruise, as it used to run.