[drover]

The carbon is a lovely mix of oil sump fumes and soot from exhaust, catch can will remove a percentage of the oil from sump but you will still get the black crud forming, highly illegal but venting the sump gas to outside means the whole manifold is just dry soot, an EGR delete is the only sure fire way but that does give other problems if not done properly ............. BUT you can also lessen the amount of soot by getting the engine up to temp quickly, no idling or engine labouring, I do think if the manifold is cleaned up of the hard stuff along with the EGR defusser cleaned of soot then a regular use of a cleaner dumped down the spout would clear away the soot and oil residue before it hardened and wouldn't give the DPF any drama but driving style/use plays a big part on how it all works.... Its a problem with all CRD's so not just a Jeep thing..

With the WG, the Merc engine just needed about $4 spent on a couple of resistors and a diode, bit of wire and bingo the EGR was shut down and the ECU thought it was still working and with the catch can fitted I just had some upper cylinder lube, no sooty sludge in the system.. sadly no one has managed to be techo enough to do similar to the VM.................... I think on these and other engines extra sensor data from other sources has put an end to the quick fix, hence the rewrite of ECU... far to expensive an option.