My daughters 92 Stanza (recent purchase) 125,000 miles, was running a little rough at idle and has a growl while driving. Also only gets 13mpg. While changing the rotor I noticed oil leaking inside the dist. I then changed the Distributor, cap, rotor, plugs, ignition wires, fuel filter, air filter, and pcv. Set timing to 15 before tdc, which it was close to anyway. Tried a bottle of Techron fuel injector cleaner. Still the same. Doesn't seem to have any vacuum leaks. There is a noticable difference when I remove each spark plug wire, so I don't think it's any one cylinder. More of a general intake problem. I am a truck driver, not a mechanic so any advice what I should check next and how would be greatly appreciated.