I dyno'd before I did a few mods and got ratios of 13.2 @ 3000 - 4000rpm, 13.5 @ 4000 - 4500, 13 @ 5000 - 5500, and 12.5 @ 6000 - 6500. Are these about right?
What should I be expecting after 5/16 spacer, z tube, and y pipe?
Haven't gotten it back to the dyno yet to get the actual readings.

 

I stumbled across this while looking at Altered Atmosphere's web site, your mileage may vary

For best gas mileage air-fuel ratios between 14.5 to 15.5 at idle and light throttle are desired. For best power (wide open and/or high throttle) air-fuel ratios on most naturally aspirated engines like to be between 12.5 and 13.5, and 10.5 to 11.5 for turbocharged vehicles.

I've read a bunch about the MREV2 and 5/16 spacer combo both here and on my350z.com and there seems to be some concern about a lean a/f condition with the combination of those two...again for what it's worth, I'm def. no expert here. If ANY of this information has helped, it was pure coincidence.

 

Thanks, helped big time.