This is the problem with the car. It is so capable, you start wanting more.
X50 is considered by Porsche as a factory option only.
The upgrade to the C2/4 cars is supposed to be done at the factory too, but can be done by the OPC.
The turbo upgrade is more extensive and the OPCs claim they can't do it.
It is an £8K option if fitted when they make the car, so it will be quite a bit more afterwards.
They change the gearbox too, so you would have to pay for the new gearbox, rather than just the differential cost, same for the turbos, intercoolers, etc.
The reason I specc'ed it was to get the stronger gearbox, which I thought would be useful later.
I think the cost from an OPC would be excessive.
If you really wanted the upgrades, then independent is the route to follow.
Although you will have no warranty cover, or goodwill. For peace of mind I would guess you either want to make sure the people fitting the stuff warrant it, or else get a third party warranty if possible (although you might struggle).
BTW - for used cars, the OPCs do not really seem to consider the X50 option as particularly saleable, and the price for a car with it, is not so much different to one without. They also do not always include it in the power output listed in the search agent, but if you look at the decription of each car, you can see "performance upgrade" listed.
There are a couple of people that can give you 500-550 with just software and an air filter.
Personally I find it hard to believe that Porsche would not be able to tell. Maybe it will pass a quick inspection, such as when you have it serviced, but if there was a big claim, I know they will look more carefully.
I do not know how to get a truthful answer you can really trust.
The other item that is a bit of an unknown, is what effect the after-market changes have on the longevity of the car. Whilst they may claim it is OK and the car can handle it, it is an act of faith to trust them. Common sense says that the things must wear out faster. Porsche tests the car quite thoroughly, and whilst there is a safety margin, I am not convinced that it can just take more power with no consequences. However, if it is not used much or you have deep pockets, then some of the upgrades look quite "entertaining".
Personally, I find that my car with just teh X50, is perfectly adequate for road use. Unless you do high speed challenges, track work (on power circuits) or need more top end power for autobahn usage, then I am not sure you are going to manage to get your money's worth out of the upgrades that you will have paid 4 figure sums for.
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