Vanguy1991G20

Hi Everyone, I need some help with this to narrow down the issue. I have had my G20 Conversion van stall twice at high speeds on the highway. Both times the ECM got super hot (enough I could smell burning electrical from it)and after the van died at highway speed the van would crank but not fire up. The first time we towed it to a shop and they changed an injector they said was bad but it still would only run super rough, they then changed out the ECM and I was able to drive home. The second time this happened same conditions, highway speed, van died. This time I had a spare ECM and swapped it out on the side of the road and managed to get home. Just wondering where I should be looking and if it has to do with a bad ground, wiring harness or whatever else would lead me in the right direction. Also considering upgrading and getting rid of the TBI altogether so if anyone had any tips for that too it would be great. Thanks