Use about 3/4 throttle in 5th gear. If it's too low at 30, you might start in 4th and shift somewhere along the way.
With the rpm that low, you're not accelerating like crazy. What you're doing is opening the throttle valve so the engine can breathe its best.
Autospeed - BSFC article
The Scangauge will be correct, up to the point where the ECU goes into Open Loop. If you press the gas pedal too much, it ignores the exhaust oxygen sensor and just dumps extra fuel in to avoid a lean mix. The Scangauge has no way of knowing
how much extra fuel, since it's not reported to the OBD system. As long as you avoid full-throttle open loop, it'll be accurate.