There's no real TUV certification process or TUV certification checking. Any US Spec car that is shipped is checked for safety and a couple of other things during registration (you'll probably still get temporary plates even if you do fail). Before I get to the next part, be aware that if you are being forced to register on a military base (most likely case), you will be held to a stricter standard than the average German. Case and point: my car is MODERATELY lowered and I had to get some parts modified to pass, but my car is NOWHERE near as low as some of the German ones I see around. If you fail, you'll have 30 days to get it fixed and re-inspected - unless they total your car on the spot, but it would have to be seriously unsafe to drive. Here is a short list of things that can stop you from getting your car registered:
Obvious saftey hazards
Rust through the body
Broken/hanging parts (like front and rear valences - some large dents have been known to prevent registration too)
Brake pads/rotors over worn
E-brake not working or loose
ANY exterior or dash light not working or working correctly
Tint on front windows
Oil/fluid leaks of any kind
Tires with low tread
Having summer tires on in winter months (you'll need winter or all season)
Exhaust too loud
Car too low (or anything under the car being too low)
Looking at your list of mods, I assume you're worried about the last two. The test pipes will probably put you over the edge on noise. Even if they don't, the fact that the front muffler/resonator is missing will probably prompt the inspectors to get the sound level tester out. I would fix that before shipping. The German standards that you will be held to for vehicle height are as follows: MINIMUM 8cm clearance for plastic parts, MINIMUM 11cm clearance for metal parts. My car was higher than that when I failed. If you can adjust your coilovers, just max them out before shipping. When you pick up your car and it passes inspection you can go straight to an auto hobby shop and drop it again.
Here is a link to the USARUER Regulation (you'll be most interested in Appendix C):
Let me know if you have any other questions or if anything above is unclear.