I am NOT an "old timer" at least as far as this site/eco....Have just installed a 2020 gen 3 in a 2014 gen 2 truck..
Not nearly as bad as a few swap,s I have done.. Nail valve buick into a vette, 471 detriot into a ford 350..cut a quad ram in half to add a bornfree body for a cummings/stick rv..great machine I still have.
But the "brain issues were interesting...
GDE was great to talk to..but had no epa non compliant tunes.. I wanted more than a tiny boost..but not over the top.
EOC was great for me.. Stage 2 plus tranny tune ..Little issues on installing but they were caused by my side..they were great on email response .
Result exactly what I wanted great driving truck. so far fuel milage 21-24 BUT I am bad on using the power most of the time..I am sure if I drove reasonably it would be more to the 24 I have seen. Art Krause