The EFI does have an interesting effect. When I cruised from Shreveport to Dallas in the hot rod I was using 17% throttle to hold 70 mph. That was 2700 rpm. I don't remember what the MAP reading was. There's a slim chance I still have that data log.

As for my turbos, they are fairly small for the engine. They spool easily. When cruising the hot rod I could open the throttle the slightest bit and watch the boost start creeping upwards. Less than 1/4 throttle would take the hot rod from 60 to 90 when going around a truck.
Add the resistance of an extra 1500 to 1800 lbs and it will load the turbos a bit more.