Originally Posted by
SASDakota
This is the exact setup I did for my father in law 4-5 years ago. His IQ failed and he didn't want to go the route of changing to their new module. So I have converted him to DSP5 and we did exhaust braking that way.
Just do as you mentioned, unplug the IQ, and unplug the speed brake module under the hood. Flash in the tune with EFI. Power down. Hook everything back up. And fire up the truck.
You need to unplug both the IQ AND the SPEEDBRAKE. If you don't, the speedbrake will keep talking over canbus and cause flash to fail.