We visited the FPV factory last week and asked this question. l was told that FPV fit the turbo and manifolds, intercooler, piping, and the heatshielding. Probably a few other minor bits l forgot to mention. The basic engine is obviously fitted on the Ford production line, but not the turbo which l found suprising. If you have options such as sunroof, 18"s, premium brakes etc then these too are done by FPV.
The XR8 also goes to FPV to have heatshielding fitted, and something else fairly minor that l cant recall. Bloody Alzheimerís!