I figured out my problem. Well, I have a solution, but still no reason.
About 3 weeks ago I asked anyone running Spetz's Test E to please PM me. A few people got back to me and I confirmed they were running the same thing as me by comparing batch #s (I didn't include the entire batch number in my post to weed out the bullshitters).
No one had the same flu-like reaction I did the day after shots.
Fast forward to last Friday and I run out of slin pins. I always used these for my TRT and used these for my cycle as well. It takes a while to suck up oil through a 29g 1/2" pin but it's so easy to pin. I dig around in my stash and find some old, sterile 25g 1 1/2" needles and 3ml syringes. Pin my glutes and all is good. On Saturday, no fatigue, no soreness.
Again, this past Monday, I hit my other glute with an IM shot. On Tuesday, no fatigue, no soreness.
I have no idea why this would be the case, but SQ shots were causing symptoms and IM shots don't. It's the damndest thing. PIP is down to manageable levels as well.
It reminded me of something I read on Dr. Crisler's forums (well known TRT doc) and that is he often sees nodules form around pockets of SQ-injected test and that this is part of the body's inflammatory process. I'm inclined to think the symptoms I experienced were part of that inflammatory process.