Yep, you can adjust both. They're almost identical in construction, only that the B-type RX-7 VAM is scaled up. Mind you, I know from experience that the VAM on the EGT is the SAME SIZE as the one on the FESTIVA.
I was shocked to find this out. I laughed. I cried.
But yea... you adjust the notch that the spring thing sets in to shift the air/fuel curve up or down. I shifted mine down so I run a leaner mix. I'm running the RX7 VAM btw.
you can adjust it with or without the car running. you use a wideband A/F gauge. If you don't have one of those, (most don't), then you have to bring your car (namely your O2 sensor) up to operating temp, then use a high impedence voltmeter to monitor the output voltage of the O2 sensor.