I would like to Plum II chimney on my 990. Also would like to delete the mufflers on it as it is absolutely annoying driving with the fan on all the time just to hear the engine. I have heard that they need back pressure or they will not run right, is this correct?
Even without mufflers you won’t hear much engine. The DPF does the vast majority of the sound reduction. I haven’t deleted or messed with anything newer than 2008 so I’m not sure what they do or don’t like.
Junkyard is correct the DPF reduces the exhaust noise and as far as back pressure that would be created by the DPF if any. Ours have no muffler just straight pipe from DPF. So I don't think you would have a problem, IMO.
I kind of suspect he is speaking in coded language here. If he is you guys might be missing the point of his question.
It has 2500 miles on it right now and I'm going to delete it. DPF is going in the corner of the shop to be reinstalled upon trade in but other than that it will be free-flowing.