I drive mostly at 4,000 to 6,000 ft, will a ECU programing help?
 

When Im at 6,000 there is not a lot of power,
will a ECU programing be of any help?

De snorkelling will help?

Exhaust?

Or all mods together?

If your car is still under warranty the dealer should be able to set the air/fuel mix to something more suited to your elevation. My REVO select plus lets me adjust the air/fuel mix. I think GIAC has a similar box. You may want to contact both of them. I was very dissapointed with the results of the ECU reprogramming. Get the exhaust and intake if you can afford it for the sound. It won't add loads of power.

But doesnt the fuel injection set the air/fuel mix ?

The car's computer controls the air/fuel mix. You can over ride the computer with the REVO programming. Check out their web site. I think the Select plus system is explained there.

The short answer is that the car's computer compensates for altitude so there isn't anything the dealer can do for you if the car is in good condition and all maintainence is up-to-date.

As far as modifications, there's plenty of info on this and other Porsche boards discussing their benefits and drawbacks.