Someone needs to be careful when selecting performance parts for the Focus SVT. Many standard focus zetec parts are not compatible.
Camshafts: I do not recommend performance camshafts for the money unless your goal is to make complete natural aspired car. The installation is expensive given the parts, labor, and custom tuning is required.
Adjustable Exhaust Cam Gear: This has show to add a few hp and torque. It is required to be adjusted on the dyno.
It is important to make sure someone obtains ones design for the Focus SVT not the Standard Zetec. The spark plugs are a different heat range.
There are many cold air intakes on the market. AEM offers the true cold air intake given the filter is behind the fog light. The others or short ram air intakes, which see hotter air given the filter is in the engine bay. The AEM Cold air intake has the best performance, but may not be as same compared to the short ram intakes if you are concern about sucking on water.
This includes performance clutch/flywheels and limited slip differential.
Any suspension part design for the 00-04 Ford Focus zx3/zx5 is compatible to the Ford Focus SVT. The Ford Focus SVT is already lowered 1/2 inches from the factory. It has 21mm front and rear sway bars. It is important to keep that in mind when making the decision on what to change on the car.
The Focus SVT already has a performance long tube equal length header form the factory. It is 4-2-1 header. See picture below.
The Focus SVT has 58mm exhaust from the factory. I would recommend going with a performance exhaust system that is 2 1/2 inches. Standard zetec exhaust will not work given bolt separation on the flex pipe is different.
There used to be many options available from Powerworks, Vortech, and Procharger. Procharger is currently the only supercharger still available for the Ford Focus SVT. There are no true bolt-on options for a complete turbo kit.