Ya, a good performance tune should be able to keep it from running ultra rich, but.... that's the question right there isnt it? Tune a VX? I remember years ago we had a member who programmed access ports for GM or something and he was gonna try to get around to putting together an access port for us to harness up to the ECU. I never did hear the end of that.
I took my VX to my WRX guys here in town to see what they thought about a post S/C tune and after 10 mins, they just threw their arms up and said "sorry dude". Damn shame cause I thought that if anyone could find a way, it would be them since they are one of the most renowned mid atlantic import tuner shops.