anguswilly
+1y
Holy CRAP.
OK, so you have to understand that a narrowband sensor is only even remotely accurate very near stoichiometric (14.7 for gasoline) - hence the name "narrowband"
This presents a HUGE problem.
While stoich is 14.7 - the desired AFR under boost is in the range if 11 (mine is running 10.5 right now till I lean it out) nowhere near where the narrowband can read - the readings you get that show you that you are near 11 with a narrowband are just random readings that are less than meaningless)
If you are going to tune the truck, you'll need a WB - or read the plugs carefully and use some other old school tricks - the one saving grace is that you have only 5-ish PSI - at that boost, it'll take longer to grenade your motor.
Really might pay to read up on meth setups - for cheap, you can make the boost safe and add HP in one step.
I hope you don't think I am trying to scare you, just trying to help.