when i cold start my car, before i put it into gear, i can see that the tachometer goes up and down about 200-300 rpms, as it hovers right above the 1000 mark and bounces between there and about 1250. pretty sure it's not the gauge, since at night, the lights dim and brighten (and i think i hear it, too...). is this normal? happen to anyone else? thanks for any input. '99 GLX, Tornado Red