it will be the boost controller, i set the cut pretty close to the set level as it seemed to have great control, id say on the highway its gettin a little creep, drop the set % down 3 or 4 points. There is a boost TP cut in the ecu but it is @ 18psi and there is ZERO chance of it getting close to that.
as for 13 psi max it is NOT an issue. as boost blleds off to about 10-11 psi from 3500rwpm on all r34's.
NO R34 has EVER made over 210rwkw on my dyno with only fmic and exhaust (more than 20 done so far), most make 190-200rwkw @ 12-13psi..... no failures as yet 3yrs on.