2002 Chevy S10 Blazer 4x4 4.3L V6

Thanks to all who helped me get through changing intake gaskets. I got the job done, and the truck runs noticeably better. I seem to have
another issue that was not present before I did the gaskets though and wonder if I could get your take on it.
The truck starts fine, runs fine and shifts fine. But if you are running along, say with the cruise set at 55MPH and 1500 RPM, and you are on a slight grade where the engine is under load, you can watch the tach drop down maybe one notch, then you feel something of a shudder or stumble, the tach goes back up that one notch or so, then it's fine, then it cycles through that same routine in even intervals.
It's almost like the torque converter is trying to go into a shift, but doesn't. I haven't driven the truck extensively to determine if the same thing could be replicated in 3rd gear instead of drive yet. I am hoping maybe I pulled a wire loose from something or didn't get things plugged back up right or something. I'll of course be checking that when I have another minute off work, but figured you all might have some suggestions.
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