DD15 emissions system maintenance

[Redland1]

My brother owns a Western Star 4900 hydrovac truck that has a DD15.It has check engine lights come up all the time and goes into a 55 mph lean mode.He doesn’t have the software or hardware to check out the codes and honestly I don’t even know what he would need since I have a Cummins.From what I have read on it on here DD tuning is garbage and should be avoided.So is there emission system tune up’s for it like Cummins? And if there is are there any videos like the one Rawze does for Cummins?