Im in the same boat. I personally am getting the car flex tuned to obviously suit both but i'm strictly only going to run E85 if im gna start it and drain the entire tank worth on a good drive or Use it for Drags, Track Etc... 98 for everyday driving for me... I've heard of 5 cars in the last month that have ruined injectors due to bad batchs of United Fuel. I dont like that ethonol attracts moisture. Some people will say man up, go hard its good.. but im very cautious of the Effect of it. Ethonols great for power, Smells great too but in my honest opinion a GTR on 98 Should have More then enough power for the streets... Honestly anything over 250 kw is plenty for the streets. Im expecting in the 400's on e85 and high 300s on 98 but meh ill stick to whats safe !