Sean if you remove the injectors then the bottom seal HAS to be renewed each time before refitting.
The injectors fit into a slight taper in the head and once up and running the heat 'sets' the seal against combustion pressure.
Find someone near you with an ASNU as there is a special tool to fit the seal.

If you remove them you cant just swap them over to try, they can be tested on an ASNU bench.

Hth Sean