Barn find. sat for a number of years full of gas. had to replace fuel pump and filter. hard starting. have to crank a long time when it does start runs rough for a bit then idles up to 1500 and wont idle down.Drained all gas and filled with 91 octane. what could make it act like it is? also put in new spark plugs. Really sharp car if I can make it run. 250000 miles, don't smoke. any ideas?