super wierd. sounds like you've done everything I'd do, in your situation.
My TPS problem was very specific at highway speeds. I would get to about 65 on the freeway, lift a bit off the throttle, and the car would stumble just once or twice and then regain its composure. I checked my TPS sensor with a multimeter and found two dead spots near the throttle position I was having issues with. I spent $30.00 on a new TPS, and it absotutely fixed the issue.
This was a pure "zero" signal type of stumble, though, like the whole computer system dissappeared into another dimension and then came back...haha. Yours sounds more like a gas tank on empty, going around a turn, and uncovering the fuel sender, "Chug, chug, wheeze, cough, varoommm....", type of thing. Thats why I immediately thought "fuel supply or spark control"
Best of luck, buddy. I'll reiterate, that you seem to have done your homework and have done everything pertinant...Its probably going to be a "forehead slapper" :doh: "right in front of you" fix..haha!