Let's start by confirming that you understand that the timing has to be set with the SPOUT removed. Next set TPS voltage at idle to .95 +/- .02. Your fuel pressure at idle is good but you need to see what it's doing under load when the stumble occurs. If you don't have enough hose on your fuel pressure gauge extend it it so that you can run it out through the back of the hood and tape it to the windshield where you can see it while driving---do you observe a drop when the stumble occurs?

Let us know.

Jeff