Hey Mr. Carver, just thought I'd stick my schnoz in here and offer a couple thoughts from a challenging situation I watched my buddy [rides a 2013 Suzy V-Strom 1000] go through throughout this past riding season.
Back in June his Strom started sputtering under load while we were out in the wilds, and it became so bad, we decided to tell the other 2 guys to go ahead and ride home (700Km) without us; I had become freshly retired that week, and had lots of time to stay with my bud another day and help him however possible.
We got permission from the motel manager, then after picking up a large drain pan, some paper towel, rubber gloves, tore his Strom down there in the sunny parking lot in front of the room we booked for another night. Tank was right full of fuel; as a foursome we thought we were all riding home that morning, but she sputtered and died a number of times trying to leave that mountain town. We extracted the fuel pump, tore it down completely, found no crud. Reassembled, checked over all the fuses, wiring bits we could think of. Still running like crap when he throttled up to a certain rev (~5K ?), - AND only under load.
Broke for lunch, reviewed everything we could online, with some tips, but little helpful insights to these symptoms. We ended up having a guy from a distant bike shop come collect the Strom with a truck, and after paying him for about 2.5hrs of his time, were still no further ahead. Buddy and I decided to just push ahead anyway, with me riding sweep behind him for over 700kms to get home. She would run fine for a Km or two, then die (total engine shutdown) - then come back to life; rinse, repeat about 200 times...
Back in his home garage, we met up again, and went through the motions of removing and testing his fuel injectors, all good. He was quite frustrated, but after getting away from the problem for a few days, he returned, and decided to trace through the wiring (again) to both the sidestand saftey lock-out switch, and the clutch lever switch.
Voila' - the sidestand switch was becoming flakey, so it was chattering open/closed/open - and as far as we could now surmize, this was most obvious under higher revs / under load while physically riding.
I do recall other contributors on this thread suggesting to check some of this ancilliary stuff, but don't know if you'd ruled this kind of thing out already?
Best of luck in your quest...