There's nothing wrong with running a copper plug in a Focus be it "high performance" or an every day non-modded driver.
There are advantages and disadvantages to both... the coppers carry better spark but the plats last longer.... the plats cost more but you should replace the copper more often.
Personally I run the coppers and have for a few years without any bad side effects.
[B]1951 McCormick FARMALL M
2007 MINI Cooper S Turbo... new project car
1998 Chevy 3500 Ext cab, long bed, 4x4, duelly, turbo diesel
2004 Harley V-Rod.... sex on wheels
2011 Harley Electra Glide Ultra Limited