Thanks. I enjoy these cars (obviously
) And the 993s have lasted 11-14 years so far
The cars were approximately 85% hand built. There weren't that many produced globally (compared to other cars of the time.) Collectors insurance means that you prove you have another car as your daily, a secure garage, and low annual miles. Rates are very good since you are not driving the car to the store, etc., everyday. You can add mods to the value, too (value is agreed upon at the beginning.)
The SAI (secondary air injection) was required after 1995 because of having to go to OBDII for emission laws. The DME/ECU for the SAI monitors whether it's functioning correctly. Because of carbon build up (or 'coking') it will trigger a fault. That carbon build up comes from burnt oil residue. That residue comes usually from wearing or worn valve guides. A head rebuild is inevitable to completely remedy that issue.
The engines are fuel injected (no "carburetor issues"), the DME meters the fuel. Fuel pump relay DMEs can malfunction so most owners carry a spare in the glove box (a $25 part that takes 10 minutes to pop into the ECU panel.) Varioram air induction began with the 1996 model onward. Very early 911s had carburetors and they did have performance issues that Solex never could seem to resolve (they later went to using Webers.)
Most all of these issues are design/component related because of the OBDII regulations. Also noise regulations. The air cooled system eventually didn't comply with newer noise regulations. It's amazing what designers and engineers have to go through over time to adopt to newer and stricter regulations throughout the world. And safety compliance too. A lot of ideal performance design has to be compromised. Unless you completely redesign the car, which most manufacturers do instead.
There's no reason to "swap" engines if you need new valve guides. These are very strong engines. Just bite the bullet and do a head job with newer guide material. Or, if the CEL and coking doesn't bother you or affect you then just keep on driving (we have strict emissions testing here in California.)
Putting a 996/997 motor in this car is not possible nor desirable. Four valves per cylinder type motors require cooling that you can't do with air. You need a full liquid cooling system. Piping, radiator, etc.. There's no point. And you've turned a last of the breed into a strange oddity.
Mods are relatively conservative with these cars. Unless you are doing serious racing. A lot of the value of these cars lies in keeping them close to factory specs. Chassis tuning and exhaust is about it. Exhaust isn't about adding hp, but getting the sound that the designers had originally intended. The 993 factory exhaust sound was tamed down for noise regulation. There was a Motor Sound Package Option 159 available. And there was also a Reduced Sound Option. Many owners get aftermarket exhaust systems to bring out the true sound of the motor. But these aren't ricer cars and so we're not talking loud fart can kind of stuff.
These cars are more about a period of sports car ownership, engineering and build quality that kinda goes back to old school days of motor racing.
Most people would rather get a modern car with 400 hp and a mfg warranty. That's understandable, for sure. I guess you have to have a certain kind of desire to want to live with a car like this. I don't really know what that is, but I can tell you that the 993 is very fun and satisfying to drive.
I've said enough
If you are ever considering one, you won't regret it.