98 A6 2.8L ECU tuning???

I've been desperately searching for an ECU tune for my 98 2.8L A6. I'd like to be able to switch back and forth between some sort of performance setting (which doesnt require more than 91 octane) and a stock setting.

Is there anyone who can either sell that sort of software for my present ECU?

Or is there a chip that i can purchase with this software loaded onto it?

Are then any flashloaders available so that i might be able to switch back and forth between the 2 setings?

Additionally, does anyone know of any automatic transmition tuning softwares? I'm one of the unfortunates that has Tiptronic and would like more responcive shifting.

Thanks all