I bet that side with the 25% off has something wrong with the o2 wiring extension...that is on there right..just the header collector pipe extension is not... Try not to get confused about exactly which extensions you all are talking about o2 wiring ext, or header collector ext.

I'm guessing your o2 wiring will not even reach the sensor so I'm sure your wiring ext is on there for those readings, so I bet that side thats 25% off is something wrong with the wiring ext.

 

I've seen blms go to 160/108 left to right for no reason other than the cam has lots of overlap, thats why i keep asking for his iac counts at idle in gear in my experience with a larger cam they need to be up about 100-110ish range. If i set my iac to the factory 40 or so counts at idle my blms will be 20 apart at idle and perfect everywhere else. The only thing that cured it was closing down the tb blades and forcing the car to run the idle air through the passages 70 seems to work with the 846. But your guess could be entirely correct, I just dont nail down that assumption based on experience.

 

yep, that could be if the TB he has does not have the correct IAC passages, there's several that do not have the correct passage for the air let in by the IAC to go thru the factory IAC holes to each runner.