well it's supposed to be 100+ RON (104?) which is what altezzas were designed to run on so it will mean the car should put out the full 210bhp instead of the 195-200ish the majority of cars were putting out on standard unleaded at the rolling road day last year. I did notice an extra bit of poke with the kit and i was apprehensive to begin with so it is worth doing in my opinion. no cheaper way of getting an extra 10bhp.
The kit is about €250 i think, i have the link to an american site that has them if you're interested i can dig it out. Probably cheaper now with the uber weak dollar.
Takes about an hours fitting and involves basically attaching to the 4 x injector connectors and earthing.
Not much to be saved in running costs, it cheaper than unleaded but you use more of it so fuel costs are about the same overall with added extra trips to the Maxol garages.
Can take an extra bit of cranking to fire up from cold so stick a gallon of unleaded to a tankful of E85 to help in that regard.
im running it 6 months now with no issues apart from the cold starting, it has never failed to start though just a bit spluttery for the first 5 seconds after firing.
there's a link on the maxol site to garages selling e85 dont know how up to date it is though hence my post above