I went through the same thing with a '92 Olds 88 a couple of years ago. Same engine, so possibly the same TPS.
Basically, all a TPS is is a variable resistor with a winding and a wiper arm. The wiper arm follows the throttle and feeds info to the computer as to where the throttle is positioned, hence it's name. You probably already know this.
Anyway, the original on the Olds wore so there was a spot where the wiper didn't touch the winding and would give an "open" reading. I replaced it with one from NAPA, and the range of adjustment was outside what was called for. My Chilton manual gave resistance readings for the adjustment on the high end and low end. Checked the winding with an ohm meter, and it had entirely different resistance than the original.
For grins and giggles, I tried one from Autozone. Same thing. I tried an OEM one from GM, and it was off the other way. The OEM was made in Mexico, the Autozone in China, and the NAPA in Taiwan (I think). Everything I tried, the Check Engine light would come back on. I don't know what was so hard about duplicating a sensor with the same resistance as the original.
I then took it to the shop at the NAPA store where I bought the NAPA sensor, and they couldn't make their own sensor work.
By bending and filing, I finally modified both the NAPA sensor and the arm that contacts it and got it to adjust where Chilton said it should be. The light stayed out. Fuel mileage improved.
Wish I had better news, but that was my experience. At some point in the mid '90's they went to a TPS that had no adjustment, so I can't say for sure on yours.
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