Unfortunately threads like this will be popping up more and more
For some reason the Police are targeting ALL modified vehicles, issuing defects and DECC notices.
Myself and my friends with modified vehicles are also going through the DECC process.
Basically you have two options:
1) Return the car to an almost stock form. (For people with heavily modified vehicles like myself this is not an option)
2) Change existing mods to comply with Engineers and IM240 certificates.
If you get DECC'd and go to the DECC inspection without any documentation, you are wasting your time and $60. The inspector will tell you the car needs to be returned to stock.
If you go there with an engineers certificate and a PASS on your IM240 test, you have a MUCH better chance of passing. Then again it is all up to the discretion of the inspector, but if he can see you are trying to pass by coming prepared and presenting a good attitude it works in your favour.
You CANNOT take the car there with mods just for passing then putting back on all your goodies afterwards, the inspector takes more photos of your car than a model shoot and are sent to the DECC. So if you are caught again you will be up for MASSIVE fines!
For vehicles manufactured after 98-00' it is much harder to pass the IM240 because new Euro emission standards are very strict.
Larger cam profiles also hinder your chances of passing as the lope on idle plays havoc with the testing equipment.
Also at present there are no exemptions for flex fuel vehicles.
I hope some of this info helps.