Checked. And check. Each MAF I have tried (four, at this point) has been a correct match.
I'm going to change out my O2 sensors this weekend, weather permitting. If that doesn't do anything, I'll try fiddling with the TPS. The only reason I think the TPS may be involved is because the issue is largely dependent on the actual throttle position.
To update the thread. Today I went out to a local guy's place to pick up a TPS and IACV. I got there and we swapped in the new TPS and calibrated it with a multi-meter and feeler gauges. In spec, problem was still there. He called his buddy who is a 20+ year tech at the local Lexus dealer. Advised to check coils. I was reluctant because both of my coils are less than 8 months old.
Anyway, we swapped in a new (used coil) and voila! Hesitation gone. Drove the car about another 70 or so miles today and no issues thus far.
Turns out my valve covers leaked oil on to the driver's coil and caused it to fail. So I stopped by the parts store and bought new valve cover and throttle body gaskets. I'll tackle those next weekend and do a thorough engine detail. Noticed a lot of sand, dirt, grime, and debris around the engine that's never been there before. Chalk it up to modified wheel well liners and under-engine cover.
So, big thanks to Darryl G. for supplying the part and taking the time to test out alternatives. He definitely went above and beyond the call of duty for a parts recycler. If anyone around the country is looking to have their ECU rebuilt, he does it for (I believe) $159 or so and offers a lifetime warranty. He also stocks all kinds of SC parts and from what I've purchased from him, offers prices better than even most FS listings here on CL. Feel free to PM me if anyone is interested in his contact info.