Hmm, forgot to mention: the turbo was having an sticky wastegate. First post above I see boost creep was up to about 1.1 bar at 7.500 rpm, but later on, with mapping it was much worse.
She saw 1.4 bar at 5.500 and rising! So we quit mapping and tried to solve boost problems first.
So, we fixed the sticky wastegate, but that was not enough, still seeing 1.1 bar under wot.
Now, because of the bad Celica intercooler design, I installed an ERL waterinjection system, with an fail safe option. ERL is injecting from 0.7 bar, because the stock wastegate is 0.6 bar. Normally, no waterinjection required with 0.6 bar or less.
So, if I (or somebody else, wife, kids, everybody uses the GT4) are pushing with 1.0 bar and the ERL is going into error, boost is dropping to stock wastegate level. Untill now that always worked fine. But with this kind of boostcreep, the whole fail safe option is useless.
Ported the wastegate now, and hope that we can map the car soon, starting with normal boost levels.