If the police take my car and make loud noises with it, all that means is the police can potentially make loud noises with my car. Not that I personally made loud noises.

The only provable noise polluter in that case is the police.

I'm sure they could also put my car on a dyno and prove it could go 100mph on the 30mph street I was on too.

Presumably for a car to be sold from factory and registered by owner as street legal in Germany, it must not be able to make loud noises under reasonable operation — specifically, driven like someone would drive a car (up to 100% throttle, up to redline rpm) but not attempting to maliciously create problems (fuzzing the pedal inputs for backfire scenarios from factory). If the police are able to reasonably operate it on a dyno to create an illegal condition, then either it has a mechanical defect, an owner modification, or a design defect; and in all three cases, the vehicle would presumably therefore not be street legal, as proven on the roadside dyno. The loophole you’re describing wouldn’t hold up in front of a judge anywhere at first glance: “I don’t ever push the gas pedal that far down in my fancy sports car designed/modded to accelerate loudly when I push the gas pedal that far down” is not a particularly convincing argument when one is found to be operating said vehicle. A more convincing argument would be, “the pedal inputs by the police were improper for operation of a vehicle and do not conform to the training given to roadside dyno operators”; and, presumably dyno logs and body cam of the operator are available to defeat that as well. And arguing that the training itself is improperly having police operate the vehicle through all factory-provided regimes would almost certainly fail (even in the U.S. were such roadside dynos a thing here!), but if your case was that the training needs to be improved in a specific way rather than for termination of the roadside dyno program, you might get traction with that.

One assumes this process is generally reserved for vehicles whose driving has earned them a dyno inspection, as it would induce mockery were they to e.g. dyno an old beaten-up Geo Metro without cause, and that the fines are directed towards either the vehicle owner and/or manufacturer, as circumstances require, as the responsible parties for its mechanical-design and/or aftermarket-modded violations of the law. (I am not your lawyer, this is not legal advice.)

Your argument holds no merit. It’s like arguing you’re a sovereign citizen, sorry does not work.

That does not really prove much. Not really clear the charges the fed had were well thought out. The general sovereign citizen test always fails because those folks still want to participate in society.

Of course it holds no merit when the law is written such that merely having the capability of loud noise is an offense, and the method by which you are convicted is the police do the thing they say is bad and then damn you for the thing they themselves just did for the purpose of convicting you.

Yes that is how society works in most places. Again this is like a ridiculous sovereign citizen argument. It’s comical to read.

Oh I am well aware. "Society" takes the things you have, uses them against you, then shits on you for the thing they have just done. Thus is how taxes are born.

But as it turns out, the government isn't society, and the law isn't what's right.