p0284 code minor engine stumble

[780powerstroke]

hello i have a 2000 ford f250 7.3 6 speed 260000 km's
my truck has a very little stumble at idle only when i gets hot.
i ran a cylinder contribution test and a year ago and got nothin.
since my ford has been for a recall to replace CMP sensor.
truck still stumbles a little at idle when warm, ran an cylinder contribution test and got code p0284 contribution 8 /balance fault.
any ideas what that means and what i should do?
truck runs good and has lots of power?

[03_Turbo7.3]

cylinder 8 injector is probably failing.. it happens last injector on the feed line takes the most abuse..

[badgti]

so is there any out come on a p0284 #8 contribution fault even after you change the injector I have one that only misfires or skips when its cold changed injector 2 months ago didn't help