Just replaced my front section exhaust which contains the Cat converters , over the period of a week my Van got slower and slower , there were no engine lights on and my OBD2 showed no faults ,but I just new that the convert was blocked , you could feel it when driving . So what a swine of a job to carry out ,first the exhaust manifold bolts were rusted solid , I had to cut them off , to do that I had to remove the complete manifold , most of the studs just came out instead of the nuts coming off , then it was time to jack the van right up and drop the cross member and disconnect the steering knuckle, remove Sensors and a couple of other nuts and bolts , even then I had to fight with the exhaust to get it out , this job took 8 hours from start to finnish , the exhaust cost 220 quid , and my van flies like it never has before , well chuffed with my efforts . So if you have a van that seems to be down on power and showing no faults it could be a blocked cat .