The guy said he ran regular unleaded fuel in it. I put 4 gallons of premium in it on an almost empty tank to make it the ride home.

I can't do much Italian work on it because I can't drive the car past 45MPH or the front end starts to shimmy uncontrollably. I had a hard time just driving it home on the back roads at 35-40MPH. I could rev the engine in neutral but that may not be good for it.

I suppose additives can't hurt. Maybe I can clean the spark plugs. Can I get away with cheapie copper tips or do they need Iridium if I change them out? It does miss at cold idle and I can feel the engine shake. It gets better the warmer it gets.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge