Low impedance injectors require a resistor pack. All LH2.4 conversion harnesses have a connector for it.
For high impedance injectors, you need to shut it off with a special (included) by-pass plug.

 VolvoResistorPack2

For 240

All 240's will originally have high impedance injectors on their engines.
If you are swapping the engine for a 740/940 turbo engine block, it may have low impedance injectors.

For 740/760/940

All turbo versions originally have low impedance injectors. The non-turbo has the high impedance ones.

Checking your injectors

If you are unsure about your injectors: you can measure their resistance across the terminals and should read 8-16 Ohm for the high impedance and 1,5 - 4 Ohm for low impedance type.
Instruction video:  https://www.youtube.com/watch?v=wi90kx32c10