Always use normal copper sparkplugs with turbocharged engines, overpriced iridium/platinum plugs fail and crack at high temps and can cause alot of damage. Cost me 8 valves and one piston to find it out for myself, one valve was completely destroyed/cut off from a blown iridium spark plug.
NGK SPARK PLUGS for your RB
gap to .025" to .031"
COPPER #BKR5E-11
I would start with the plugs they are like 2.50 each if that dosent fix it then swap around the injectors.
And the injectors are not that hard to swap. Just pull the rail (carefully) (3 or 4 bolts i think) and juggle 2 injectors (relube the rubber grommets with vasaline).
and if it is failed RB20 injectors are the same as KA24E injectors. You can grab a grommet kit from autozone.
For good info from lots of people that have been down the rb road go here nicolub rb forums