Egts can be tricky to explain, but the two biggest contributors to high egts are too much fuel and a restriction of air flow. The reason why you hit a brick wall past a certain point with these turbos is the hot side wheel. The cold side which compresses air into the intake, is big enough to supply 26-27 psi, especially with the 60-1 mod, but the hot side cannot flow enough exhaust to support that kind of boost level. You start getting higher egts because more and more exhaust gets left in the combustion chamber, not allowing cool, intake air in. This restriction for the intake air brings your boost level up. This is why boost does not equal a higher power level, it’s just a measurement of restriction in the intake. I am making more power at 14 psi now than I was at 26 because of this.