Take the car to a dealership and have the issue diagnosed. When something is blocked, you will definitely feel a change in the performance of the car, not smell it. If there is no real change, then the problem might be something else. There is a fanatic who had the same issue as you did, not long ago and it turned out to be a diesel/fuel related. Do not go and waste R8k on down pipe and software if you don't really need that.