E85 flex fuel
 

If I am tuned for E85 and in the future decide to get a flex fuel kit would I need a new tune?

Yes

What he said. Whether you have a dual tune for pump and E85 with switchable maps or have a designated tune for E85, you will need a tune that adjusts the fuel maps and timing based on the ethanol ratio. If you didn't do that then when you ran E35 you would be dumping too much fuel.