High Fuel Pressure---Help!!
 

I have a fuel pressure gauge installed in my car and have had it for a couple months now. It was reading very erratic values for some time (between 60-80 psi at a given time). I ordered a new fuel pressure regulator and voila the pressure was back down to a consistent 60-63 psi and when I pressed down hard it went as high as 70 psi and then fell back down to 60 when I let up. Now it seems to be reading erratic again and goes as high as 80+ psi on start up. When I am out running errands the pressure gets to 70 psi and sits there (only going 60km/h in 3rd gear). Not sure if this is related to the fuel pressure but whenever I hit the accelerator, whether I am accelerating from a red light or moving slowly in stop and go traffic, and the rpms drop down as I let off the accelerator to lower than normal and then pick up again then stays at a normal idle (approx 700 rpm). Every time, without fail.... If anyone has any ideas about the fuel pressure or idle issue please let me know it is driving me absolutely insane especially the the fuel pressure issue. TIA

Try a different fuel pressure gauge. A Boxster normally varies between 3-4bar (40-60psi). It is more likely that your gauge is reading incorrectly than you have blown out 2 fuel pressure regulators.

As to your other symptoms:
Any CEL error codes?
Model, year, mileage?
Any recent repairs or mods done?

I will try a new gauge sensor and go from there. It is a 2001 base with 155k km's. I have recently added the sensor itself along with idle control valve (used), 74 mm TB with IPD plenum.

A small intake air leak as a result of your recent TB/Plenum work would explain the idle stumble at high vacuum. Retrace your steps.

Could an air leak cause the fuel pressure to fluctuate like this?

Fuel pressure fluctuates whenever you go from idle to full throttle. It is unrelated to an intake air leak. You already changed out your fuel regulator so at this point I believe you have eliminated that as a failure point.

Is it a oem fuel pressure regulator or aftermarket?

It is oem purchased from pelican part number 993-110-199-01-M14

It appears that the leak was effecting the the fuel pressure because the leak was coming from a rubber sleeve on the right side of the resonance tube. On the left side of the resonance tube is where the air hose plugs in from the fuel pressure regulator which is why I think it was reading the fuel pressure so erratically. Once I temporarily filled that leak the idle was dead still and the fuel pressure was extremely steady and consistent. Not sure if I have any other leaks so we'll see how this goes for now.