The B58 has some unique tuning challenges including an IPW limiter built in to the DME logic. The AFR and tuning the JB4 runs is perfectly safe for the vehicle. As proven by several 1/2 mile events beating the crap out of it. It has lean spool mode down low along with multiple injections per stroke then AFR should be in the mid 13s at higher RPM. Which is the same as all of the F series N55s. On the F series N55s many are running 500whp+ with larger turbos on those air/fuel ratios for tens of thousands of miles with perfect looking plugs and no issues.
