Hi, there lies the problem, most of these mobile people, Techs shall we call them, arrive and plug in take your money and clear off, normally they are considered cheaper than say a static remap company, which they are they have no premises to pay for and often as not have just a basic software program and not the same tailored software platform as for example Blufin, if you buy from them they will go through extensive questioning of what you expect and then give you realtime options of what you can realistically achieve as per the milage on the vehicle, you then get a loading device and its normally a ten minute job to load it via the OBD port, all of their software programs are checked for quality before they get to the end user and the advantage of their system is that you can upload the mapping back out, yes these types of companies are more expensive but what you get is bullet proof technology.
If the mapping is working ok just buy another EGR valve and fit it and leave it there, if you block it in another few months you will probably start getting some more codes/lights as the ECU will have worked out there is no gas flow and thats why the EGR is not sending it any data to tell it when the valves open/closed because the valve is jammed in a ton of soot where its backed up past the blanking, mapping out changes the command protocol and tells it to stay shut, the other down side is my mate did it on his transit and over miles the red hot gass melted the blanking plate and allowed the super heated gas into the engine bay which in turn melted the fan housing at the front, remapping is a multi faceted industry and if you go mad with it power wise it causes horrendous and expensive problems which I have personally witnessed on some occasions, it comes down to the old saying, IF YOU WANT FAST,BUY FAST, believe me its cheaper in the long run.
Steve.