GTI sounds like you have the Zetec 1.8i 16V.
If so Ford replaced the original platinum plug AYFS22F1 with 1mm gap for the non-platinum AYFS22CB with bigger 1.3mm gap. Should work although when placed in a Focus the higher voltage for this gap can cause to break the coil.
So for safety bring it back to 1mm.
Last edited by YBJ; Nov 19, 2011 at 06:24 PM.