I have a procharged 4.6 2v GT. Since adding the SC I have been having problems with the#4 spark plug closing up when I get on it hard. It is kind of wierd, but it only happens when I get on it hard. The car was set up on a Dyno after the SC install and runs fine most of the time. It has done this three times now, and I am starting to think I have a foreign object in that cylinder.
It is always the #4 plug, and the electrode closes completely so that no spark gap remains. Anybody had this issue?

 

What type of plugs and what heat range are you using?