Ok guys here is what you need to know....

The nav radio is different that the one in Porsche and the Becker units sold outside the US and older units.

In the past companies were able to flash the removable rom chip to allow the cd changer port to stay alive (meaining it did not require a data stream to open the input). The crossfire radio and ones developed around the same time nolonger use that design.

the aftermarket and Porsche radios were designed not to need the data stream as the inputs would function as either an aux input or for the cd changer based on the radio menu setting.

The Crossfire radio requires a data stream to keep the input port open. In other words it needs to think there is a cd changer connected to it and a cd is playing. The only company I have seen so far that has developed a product designed to fool the radio is http://www.solisto.de

The reason FM transmitters are hit and miss are the fact that many companies at the launch of the ipod craze and XM/Sirius developed products with output transmitter power in excess of what the FTC has deemed legal. Over time and with some compaines getting caught, products came into spec failed to deliver a strong signal. OEM systems with twin tuners (ours) and diversity systems (nissan and some german cars) typically have a difficult time with FM since their systems look at two different signals and hand off based on which one is stronger. If your ipod signal is weaker, it is overcome by the other signal and you begin to hear noise.

An FM relay pack inline with the ant, is one way of getting a better signal into the radio and they typically are designed for the product they are sold with or work with. Harman Kardon Drive+Play and Drive+Play II are good examples. You can used an FM modulator in line, these are typically how rear seat aftermarket entertainment systems are done, not perfect but better than the smaller broadcast types.