Designed for racing spec purpose only
R7420 spark plugs and older platinum/platinum plugs versions.
I have not validated it but will check plug length of stock type plugs.
Other types of plugs (cheap shit versions) NO!
IF you run these then you are not the kind of person who would pay for my quality items anyway
so it was never designed to suit that market.
Other aspects a few people are checking out RE: PS and AC etc