GTR miss fire problem

[7heavn]

Lucky me I've got a miss fire problem now in the GTR. Pulled the plugs they looked alright cleaned them and put them back in also borrowed a couple of coil packs and tried changing them around but hasn't seemed to solve it .

It has a miss on idle and under load but only when cold once it gets up to temperature it clears itself and is fine and stays that way all weekend . But after it sits in the garage during the week and you go to start it up the problem happens all over again .

When it first started occuring I pulled the plugs and number three from the front was alittle bit black but after cleaning it and throwing it back in the problem was solved . It did happen again so I tried replacing the plug with a new one and it was good for awhile but now it's back and after pulling the plugs out yesterday they all looked ok but cleaning and replacing didn't solve the miss .

Could it possibly be an injector problem ?, I'm running aftermarket 550's but don't know how old they really are . Any idea's you guys could throw around would be good