Today I took the number one and two injectors off my car to have a look. On the bottom there was a build up of dirt, not on the nozzle itself but around the bottom area under the area of the o-ring. Does this mean that the injectors are dirty and need cleaning or is this normal to have some dirt in this area.

I pulled them off becuase the car is using to much fuel at the moment and it has a rough idle.

mate i reccommend having your injectors cleaned, I had mine done and the throttle response has increased dramatically, it go rid of that lag when you floor it, I have the same rough idle, so the mechanic suggested the clean, still got the rough idle after clean, so I didnt have to pay for it, But it sure does make a difference when Im playing hard.

see a mechanic about having a carbon clean done.

that will clean the injectors and also clean all the carbon build up from the valves, pistons, chambers and ports

cost me 120 to clean my injectors and get new o rings and the dude even re sprayed the injectors lol!

get them flow and spray pattern tested , ultrasonically cleaned new filter baskets, orings and spintle cap, then re tested get all the crap from inside of them