i got the same problem at transition the ower dips also on boost gauge it drops to 6-7psi then gets back up to 10-11psi could this be altitude like you said wankel i drove car in arizona and had no drop in psi everything was nomal?

 

did your pfc displayed 12psi or your boost gauge??

 

My boost gauge read 12.5 PSI, The PFC read a max boost of .80 Kg/cm^2 or 11.4 PSI