Zetec plugs are kind of weird. They have a long reach into the cylinder and almost no other plugs have the same threads and reach. The only stock replacements that are copper and colder are Motorcraft AZFS22C. They are copper and one step colder. They are a bit hard to find and usually will have to be ordered from the dealer for around $12-15 for the set.
Basically, one step colder for every 40-50hp. But again, only one step is availiable over the counter. You can get custom plugs up to five steps colder at
www.focus-power.com, but they cost $50 a set, they are machined by hand.
You mean like you said your MAF and fuel pressure mod was just fine and a week later you blew your engine? While your quick engine swap was impressive, the need to do it wasn't surprising to me because of what you were doing.
Becareful. Read the FAQ.
