Nissan Elgrand E52 Lowdown

For anyone starting to look at a Nissan Elgrand one of the first things that you will find is a million discussions about cats and whether to have them decored.  Not sure about you, but it was quite confusing when I first began my search.  If it helps, lets start with a quick recap: On the older model E51 Elgrands, their exhaust system has four catalytic converters, lined up in 2 pairs. There are two front cats and two rear cats, prior to the muffler and exhaust pipe at the rear of the car. It seems that there is a chance that due to ECU errors and excess fuel getting injected, that some unburnt fuel in the front cat can cause it to break down.  When it breaks down it can cause debris which will move from the front cat to the rear cat.  There is then a possibility that the debris in the rear cat could block the cat/pipework.  This in turn will mean the engine cannot expel the exhaust fumes, and some complicated process can then cause the engine to self destruct....