Art,

I have been using Autolite (now Tempest) URHB 32S Fine Wires in our stock IO550-N for 310 hours.  They finally required cleaning (got a little hard to start) but they were not all that dirty.  The gaps are still in the .017 to .021 gap range and the insulators are a nice tan color.  We run lean of peak most of the time.  I like em.

Steve Colwell   Legacy