Your results are interesting since I'll be pulling our ~9k lb 5th with a 6.2 super duty rather than the ecoboost. I understand you're not at WOT but it's running up to 4k so there is a fair amount of throttle input.
Your 30 second 0-60 is about what my old GMC 5.3 and 7000lb TT would do at moderate throttle and 4k RPM shift points. If I pushed it, 25 seconds was about it.
My ecoboost would get the same trailer to 60 in about 17 seconds without even sounding like it was working and not exceeding 4 grand.
With our 8800 lb 5th, the ecoboost could hit 60 in 20 seconds or a little better.
I'm anxious to see how the 6.2 and 9k 5th fit in there. I know it's not a race to the campground but for me, towing is the best part. The 5.3 setup was not fun at all so I hope the new setup is somewhere in the middle.
