What is the firing sequence of a 1990 Saab?

900 or 9000?

It should be cast into the engine block and/or the head.

1-3-4-2

On the 900, the #1 cylinder is closest to the firewall, #4 is at the front of the car closest to the radiator.

Front wheel drive vehicles have transverse mounted engines so cylinders run in line with front wheel axis.