I would think that despite, as you say, even they may not catch everything, your best bet will be to take it to a GM dealer and likely pay a little more.
Incidentally, I had a strange experience with our 2008 Duramax last Fall when the truck suddenly went into "limp mode" when towing at 65mph+.
Speed suddenly dropped to maybe 5mph - a bit scary since I was in the fast lane on an interstate at the time!
The dash message said "engine power reduced" then "change fuel filter." Fuel filter life monitor dropped to zero but had been 53% earlier the same day. I suspected maybe I had gotten a bad load of fuel from a small gas station where we filled up earlier in the day.
We managed to creep along five miles to a town with GM dealer. They changed the filter but said the fuel looked ok so they didn't drain it.
They couldn't explain what had happened and if the filter was really bad or not - said it could have been a computer glitch. Anyway we made it home without further problem.
Hoping I don't experience that again, but now I carry a spare fuel filter and necessary tools as well as an OBD II code reader / resetter. This is just in case it happens again in a more remote location, I could maybe deal with it myself - or at east have the filter on hand if we need to deal with a corner garage.
There are Youtube videos showing how the change the filter and re-prime the system. Doesn't look that difficult so I think I could do it on the side of the highway if I had todo so.
Hopefully I won't have to!
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.