Congratz on your Z, and welcome to the
Brotherhood of the Beast!
I agree w/ Scott & Glenn; taking a logical approach - and it sounds like you are, so far.
A Tech 1 approach is a good place to start, OR, have it scanned at one of the many auto parts stores
that can do OBD-1 scans
The Throttle Position Sensor (TPS) is located on the left side of the throttle body. I would want to pull the connector and read the resistance through its entire range, making sure resistance change throughout is smooth and unbroken.
Both fuel pumps come on initially for a few seconds, and then the secondary pump shuts off until load conditions are met for it to be switched back on. This will result in fuel pressure reading, more or less "normal" when performed w/o starting/running the motor. But, under actual driving conditions, a failing primary pump scenario matches your symptoms "to a tee" (as the secondary pump comes on to "rescue" the primary pump as load increases).
Dynamic fuel pressure test... Taping a fuel pressure gauge to the windshield and going for a drive puts a finger on a delivery issue very effectively.
If you don't already have one, for sure you'll want to get the Factory Service Manual (aka FSM). AND, I'll say that my scanner has paid for itself many times over. (I'd kill for a TECH I, but even my little 'ol AutoXray has saved the day many times. Beit a TECH I or a Snap-On or whatever, I highly recommend everyone have one!
)
P.