Just sell the car and you wont have to worry about it!
I might not run one on only a stage 1 tune. But its been done without much for ill effects except some backfiring. Might not happen as much with your car having 2 factory cats. A catless/high flow catted DP might make it worse.
You can do what you want, Ive read articles for and against it. Most say it will run rich in between shifts, but its SOOOOO quick that it will most likely do nothing except throw a tiny bit too much fuel resulting in the occasional backfire.
I wouldn't run anything more then 50/50.