Working on a friends turbo Silverado with an E38 PCM. I don't have a ton of experience with them, mostly LS1 PCMs... I am thinking that it has a mechanical issue causing the stumble/miss and unburnt fuel is showing up as spikes on the wideband. It is plenty rich right before it happens and the spikes are sporadic and very large - not typical lean tune characteristics. Any help ruling out a tune issue would be appreciated! Tune and log attached.
Thanks!
Bret