Whats the best spark plug to use in my mach?

 

When I had my Mach 1 tuned by Danny Swanson of Swanson Performance, he recommended NGK Stock Number 4177 TR6 (SKU 87295 04177). These are regular copper core plugs that are colder than the OEM plugs. A lot of FI guys run them and Danny recommends them for normal aspirated tuned motors, too.

I've been running them for 20,000+ miles with no complaints.

 

I switch between ngk and motorcraft