ive been using premium, 91. recently seafoamed it, im in the process of putting in sd headers, i have the read and front and cross over out. The valve cover gasket in the back has been replaceed and i just also replaced the back 3 spark plugs, dude these were shot! the gap and..omg, like cant explain what i seen, but anyways, day by day ima slowly put the headers on, and then put everything back together, reroute the vac lines( new lines and make them more neat, and work from there. I possibly might do a tranny service on it. I'll keep you guys up to date on it. But before i took this apart, on the way back from work, shut off on me at a light, my mileage has increased in 14 mpg (: yay! -___- idling is even more stable, well its always been stable its just now its...better? haha. What are the steps on replacing the fuel filter, i might as well. pull the carpet from trunk and its in a lil opening? something like that.