GMK stands for Grand Master Khan (I think thats right).
Its an extension piece (long radius 90 degree bend) that attaches to the CTA (or any short ram) intake that relocaes the filter into the fender.
Requires drilling a hole for the pipe and relocating the fuse box.
The CTA extension for the ZX2 is the same thing.

Frank McCoy aka Mod-deth aka Mid Life Crisis aka SVT Doood aka mcgainer is a SCAM ARTIST Pre98 Zetec - Some Mods