Air fuel control derate?

[CSteffler]

I’m have somewhat of the same issue with my 08 t800 with an isx600 right after starting it up the idle jumps from 600rpm to 8/900rpm and will not come back down, driving it and it has no power until you eventually get the rpm above 1700 then everything is happy, had mechanics with insight so injector cut out test, checked fuel pressures on insight and mechanical gauge, checked the turbo and actuator, cleaned the timing and metering solenoids and swapped them from front to back, tried another ecm which fixed the idle problem but not the low power problem.. fuel filters changed as well.. at a loss here any help appreciated