I'll be sure to do another test run with the gauge and log the MAPthis time

Are you saying that even if MAP=0 at WOT, and my pump is dropping off a few psi under load, i should be looking elsewhere to solve the high rpm cutout problem i have?

 

Depends on how much HP you are making, and what injectors you are running. If you're running out of injector, a 4% loss in fuel flow can be a serious problem. It going to cost you a 1/2 point on A/F ratio.... a well-tuned 13.0:1 will turn into a 13.5:1.

 

I did some logging and it looks like at WOT im pulling a vacuum between 1 and 3 in. Hg, depending on the rpm. That should be somewhere around 1 psi average. So, the WOT pressure difference between my fuel rails and manifold is on average 41 psi. Thats close to the desired 43.5, but it sounds like my pump isn't performing as well as it should.

On a separate note, does the vacuum at WOT mean that i could benefit from a bigger throttle body? I'm using the stock 48mm tb and i have a factory ram air system w/ a K&N filter.

 

Hey, just my .02......I chased a VERY similar problem on my 95 Z28. It was the battery! When we did a load-test on it, it was not at peak performance....$89 later & A-OK!

 

Injuneer is exactly correct. The FPR is not bad if the fp is going up to 43.5 or there abouts when you disconnect the vac line.
In order to determine if the fp is getting weak and not able to keep up, you must first make sure you have near barometric pressure in the manifold at WOT. You could just be choking the motor by not having a big enough throttle body or intake ducting to bring the manifold pressure to barometric pressure.
On the other hand, if its the original pump, I'd go ahead and replace it, a 9 year old pump is a worn out pump in my mind, not to mention the pump sock is probably full of stuff and clogged for WOT applications.

Also, as mentioned above, the voltage may not be up to par at the pump, thats where the Racetronix fp harness comes in handy. It runs a thick gauge wire from the alt to the pump instead of using the thin gauge factory wiring.
And on that note, I'm actually replacing mine this weekend.... Did the harness last weekend.