I spoke to a German mechanic the other day he specializes in VW AUdi BMW Mercs only , I broached him about EGR blanking DPF etc . He was very knowledgeable about possible problems that may occur down the track after around 20 to 30thou km after the mods are done . Apparently the EGR and its cooler is designed to keep the engine operating temp in a very defined range , without the EGR that will change and over time can lead to piston failure .