These cars are meant to be driven. I have found the subject tuneup to be especially effective on the spark free engines. My car gets this treatment at every opportunity without the use of additives. Long grades work best for raising the engine temperature to the point where carbon burns off. A big benefit of long grades is that the engine can get the required workout without attracting unwanted attention. Long on ramps can also be advantageous if the engine is already up to temp.
1st In Class - Starfest Concours 2004
1st In Class - StarTrack Concours 2003
MBCA - Niagara Section