2009 Cayenne GTS fuel pump problems

It does sound like vapor lock, as Jim said. You can try insulating your fuel lines, especially on top of the engine with foam made for pipes, and then wrapping in foil. Other than that, you might have to re-route the lines further from the engine heat. Use caution when re-routing lines, you don't want a car fire.

I have the same problem with a 2008. I was driving across Kansas yesterday in 80 degree weather. I was averaging about 90 mph. The engine light came on and the car would cut out briefly about every 30 to 60 seconds. I could maintain about 75 mph and would drop only a few mph each time. I could not use cruise control. I had about 1/4 tank of fuel. I stopped at a gas station and filled it up and never had another problem. I had the same problem 2 years ago and Porsche replaced the fuel pump. When it happened a few months later, they could not figure it out and refused to replace the fuel pump again. I don't think they believed me, even with the codes saying I had a fuel problem. It has not happened since but this is the first long trip I have taken since then.

Sure sounds like vapor lock. You could try mounting an oil cooler away from the engine and run the fuel from the back of the car to the cooler and back to the rails, keeping all lines as far as possible from the engine. Use gas line only, preferably braided, double clamped or A/N fittings. Insulate the lines with foam. Safety first. This should work, but be careful. Good luck.