I kill the engine, the fans are still running (flex-a-lite running for 30 seconds after shutdown), but then the temp on the cluster jumps to 260. When the fans shut off, the temp goes back down. So how does that happen?

 

Because your water pump is not spinning when the engine is shut off. The fans are cooling only what's in the radiator, not the block.
It's normal...

 

Um... yea... i know how that works. But why the temp sensor jumps to 260 only when the fans are running doesn't make sense to me.

 

Because if the fans are running, it's HOT. They're not gonna run when the coolant temp is below their cut-off temperature. Your gauge is likely not accurate and the temp is probably actually closer to 225 or 230...

 

They only run when I want them to using the flex controller. But I don't think you understand what I'm saying. Why would the movement of hot air from the fans around the engine bay cause the temp the sensor is detecting go up... The water pump isn't turning, the engine is off... everything is off, and the temp gauge is at 220. Then I turn on the fans manually, and it jumps to 260. But whatever.

 

I'm tracking with you.

I would guess that the gauge has some kind of issue, similar to how the tachs in these cars can point to a random point after shutoff. Something in the current draw of the fan might be feeding into the gauge wiring and making it peg.
I'd check your grounds, maybe check the wiring behind the dash and make sure there isn't something with the insulation rubbed off or something.

 

Agreed. Sounds like an electrical issue to me.