Hi, My 93 gas gauge stays on full after a complete fill up. Drove over 200 miles with no change. Added Techron in the tank and drove a while with no change. Any ideas Please? Thanks. 

sounds like your sending unit/float is either stuck or took a crap , they are real easy to get at , the whole unit comes rite out , its just under the gas fill door some real good u tube vids on it , good luck !

I had the same problem on my '92 and as HockeyJeff suggests replacing the sending unit fixed the problem.

There is a better way to go that I learned from the marine guys. A few years ago, I filled my tank with fuel cell foam to stop the slosh (which is significant given the tanks span the width of the car. These use a tube that is based on capacitance to generate the signal and therefore no moving parts. It is just an aluminum tube about 3/8" diameter that I ordered with the right resistance for GM gauges. That said, I had to build a custom cover plate to mount it and the other fittings. Works great though.

Here's a link with some.

https://rochestergauges.com/products/fuel-level/capacitance/