engine light on Help please

Car : 2004 Pajero Exceed 285000kms

About a month ago whilst traveling the engine light and the 2 traction control lights came on as i was pulling into dubbo nsw. Around 1km down the road was the mitsubitshi dealer so i pulled into there and the lights went off. So i thought it may have just been a once off so i continued on towards the zoo,well just as i stopped light came on again, so off to the dealer i went. And again as soon as i got there light went off.
The dealer put my car onto the computer and it came up with an errorr 41 code to which he said could be a list of things. the first thing he checked was the fuel filter to see if there was any water in there due to bad fuel (nothing) he than checked few other things and reset the computer and went for a drive and the light came back on.He said it could be the diesil injector pump as my car has 285000km on the clock. He than rang up mitsubishi to ask what else he should look at.They said to check what he said to me was the carbon filter (not sure if this is right) he pulled it out and said it was blocked, he cleaned it out and reset computer again and went for a drive and this time no lights came on. He said this may have been the problem and said see what happens.Wellfor the next 1500kms
The lights didnt come back on and all was good. So when the lights did come on i noticed that the idoling of the car had dropped a little (not affecting anythnig) and on the freeway it doesnt drop into overdrive till about 130km/h instead of around 100-110 as it use to. now the lights dont stay on all the time they turn on and off only every now and than.
Sometimes when the lights do come on if i pull over and put the car into nutural and let it idol they turn off and all is good.
The car hasnt lost any power nor is it blowing any smoke.
I think i have explained the problem the best i can.
Hopefully there is someone out there who can help me.

Cheers
Dean