hi just did a big trip to adelaide , found the trip computer to be out in usage by about 1-2lt (over)
this is throwing the lt/km average out to , anything i can do to get it right is there maybe a faulty injector or something similar
thanks

If you've done the calculations for actual consumption which it seems you have, then the injectors should be fine as a faulty injector would affect the actual consumption figure.
I had an injector that wouldnt close effectively and the fuel line would bleed off all pressure in about 20 mins, which in turn made the car hard to start as line pressure would have to come up before the injectors would work properly, it also smelled richly of unburnt fuel at startup..
It used a bit more fuel while it was malfunctioning but the other symptoms are much more obvious so I'm leaning away from injectors specifically.
Maybe it's just a bit off with the level reading from the in tank sender, but I'm not sure if the trip comp uses this input for it's calculations.. Maybe give a mits workshop a call & see if it can be calibrated?? Maybe it's a problem with a sensor.. Not sure, but doesn't sound like injectors! Hope this helps a bit!