The biggest portion if you are going to do extensive exhaust work is the sound. You have to meet the USAREUR Registry of Motor Vehicles 95db sound test IF the inspectors deem that your car. Here is the link to the regulation to better help you. Only good thing is that on base, they will not smog check you
Also shoot a PM to KC Skyrider. He is currently stationed in K-town, on Ramstein AB and can give you more detail in regards to inspections. Also download AE Reg 190-1, that is the USAREUR/NAVEUR/USAFE regulation regarding vehicle inspections and get very aquainted with it and know it from front to back. The inspectors on Pulaski are D*CKS (mix of German and AF people) and will make your life impossible inspecting your car, specially for height since thy are supposed to follow the reg and they also follow portions of the German TUV. One thing to note is on ride height, if your car CANNOT clear 10cm from the lowest hard point of the car, they will fail it.
If you have any questions or need any info let me know. BUT DEFINETLY DOWNLOAD THE REG!!!!!