Re: tuning a 2006 cayenne turbo
Drive the Turbo S - this will give you an excellent idea of what it will feel like.
7K is on the higher end for the three things you want to do.
An ECU tune from Revo is about $2900 with a handheld fllashloader.
From GIAC it is about $2350 for a similar setup - (stock and performance/pump)
For a FULL exhaust it is about $2500 from Evolution motorsprots.
For Fabspeed catback exhaust/sport muffler and cat bypass pipes it will run you about $2600.
For performance filters (BMC or K&N) it should cost about $150-160 for the pair. Better yet, Evolution motorsports is coming out with a superior product called "Evo - V-Flow air intakes".
These mods should be done by a mod friendly Porsche dealership - who will back you JIK.
As far as resale is concerned just keep all your stock parts and replace them prior to selling. Bypass pipes and sport muffler for instance are interchangeable with OEM pipes etc.
Evos air intake reguire no modification and bolt on and off quickly.
Try and find a dealer, same dealer, that flashes the ECU/DME.
Also some companies offer a "trial" period for computer tuning where you can just go in for the tuning and drive for 4-5 hours and then it "returns" back to stock. If you like it then you can buy it approach.
Everyone, absolutely everyone, that I have talked to locally and on other forums have loved these mods, noticed a difference, and NEVER had any service issues or warranty problems, and traded in cars without consequence either - at premim prices too.
Back to the 7 large, if you include install you are probably right on target.
I will have completed the mods you seek by the end of the day tomorrow so I can tell you first hand if I feel a differnce.