I've done my decat and EGR blanking and have noticed no change in engine note, no change in fuel consumption (I measured it accurately before and after) and only the very slightest perceptible change in performance.
I think it comes down to, is your cat collapsed, if so then its a restriction on the exhaust and the decat improves it. If the cat is not collapsed then no change. EGR: if the EGR valve is working fine, no change. They get bunged up with carbon and don't seal properly, blanking this off makes the difference.
I think it comes down to, is your cat collapsed, if so then its a restriction on the exhaust and the decat improves it. If the cat is not collapsed then no change. EGR: if the EGR valve is working fine, no change. They get bunged up with carbon and don't seal properly, blanking this off makes the difference.