According to the FSM, each injector is installed in the fuel pipe. A bolt from the fuel pipe is removed, and replaced with a special bolt that adapts to a fuel pressure tester.
Other include a Schrader test valve, to simplify getting a fuel pressure reading.
This is a link to a fuel pressure gauge that can be installed under the hood:
Fuel Pressure Gauge Kit 2RZ/3RZ
At the bottom of the linked page is a replacement fuel pipe bolt, which is part of the gauge kit. If an under hood gauge is not wanted long term, a Schrader valve should be able to be adapted to the replacement fuel pipe bolt. This combo would make for a convenient test port.
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02 4Runner SR5, 2WD, 250k, kid's car
98 4Runner Base, 2WD, 2.7L 4cyl, sold at 264k. Great truck, but the 4cyl just doesn't have enough power