I have a mercedes s430 Scotty, I do all the work myself. All good and it isn't killing me for that reason only! Anyway, son-of-a-gun has slight rough idle. I've changed: fuel filter, plugs, wires, thoroughly cleaned MAF sensor. not much improvement. No codes or misfires. Could it be the harmonic balance? Man, I hate to be a parts replacer and my obd scan tool either I don't know how to use, or not sophisticated enough.. help?