That may be another reason you aren't getting good smoke flavor. That will block smoke absorption. Trust me the bark will form without searing first. If you like a good crusty bark, don't foil the butt. As far as injecting goes it really isn't necessary in my opinion. If you cook the butt correctly it will be tender, falling apart and juicy.
The point of injecting is not because a pork butt isn't juicy or moist. It's an extremely forgiving cut of meat and rather difficult to not cook properly. The advantage of injecting pork butts is you
are adding flavors deeper into the meat where rubs and smoke will never reach. Stepping out of the more traditional forms and/or processes can sometimes yield surprising results.
And of course like all things smokin', it's just a matter of personal preference.
I don't think searing is going to keep your smoke from penetrating, searing is common practice with some folks. I'm not familiar with the MES, but isn't the A-Maze-N-Smoker so popular with
the MES owners because it delivers a more consistent longer smoke etc?