It seems electronic engines will give you the rise and then shut off fuel. I have noticed it between our TR98 and CR970. Once an electronic engine gets to its preset peak, it will shut off fuel and fall on its face. Your chipped 2388 probably kept dumping fuel.
A wastegated turbo is much better because it will develop more boost at lower RPM or lower load (in the case of a combine) but will not overboost in applications of high loads. In a nongated application, there would be lower levels of boost when the machine isn't full, requiring the turbo to spool up for slugs rather than having boost all the time. There is probably some adjustment there as well, but extra boost without extra fuel is useless.
A wastegated turbo is much better because it will develop more boost at lower RPM or lower load (in the case of a combine) but will not overboost in applications of high loads. In a nongated application, there would be lower levels of boost when the machine isn't full, requiring the turbo to spool up for slugs rather than having boost all the time. There is probably some adjustment there as well, but extra boost without extra fuel is useless.