People usually use 1.8 ohms on a 306. A fuse will add several milliohms. I used two 1 Ohm resistors in series (equals 2 Ohms) for testing and it worked. Everything in that range will be okay.

Do you know if it is the seat belt pretensioner or side airbags? Is the warning light blinking or permanently on? I would rather fix it than doing the workaround. Clean the contacts with brake cleaner and bend the metal tabs in them. The seat belt pretensioner has an orange plug and the contacts are round and of small diameter. You will need a needle to carefully bend the metal tabs of that connector. It worked for me. Wouldn't hurt to do that on all connectors under the seats. Last solution would be to cut off the connector and solder the wires together.

So neither of the plugs are connected? Weird. If they are disconnected, the lamp should stay on. Could be that a previous owner already put the resistor somewhere else in the wiring or directly at the airbag control unit and that it became loose.

If so, you would need to completely take out the old resistors as you could blow the airbag control unit if you put in another resistor. (1,8 ohm / 2 = 0,9 ohm)


EDIT:
306 HDI seats? HDI should be Phase 3 and should not all phase 3's have side airbags?