When engine cuts out @ 3000rpm it suddenly looses power output and this will be very noticeable. However rpm would reduce to zero slowly as the car reduces speed especially if you have a manual tranny. During these moments the tach should still record rpm's and would drop slowly as the engine slows down. However as I stated if you loose primary ignition pulses tach will drop to zero instantly. An important key to your problem is to understand what the tach does in relation to actual engine speed.