The best car adapter...

If you're using a cassette adapter, changing how you connect isnt going to improve interference. Quality maybe, but interference will be picked up by the headunit/speakers no matter how you connect. I get interference occasioanly when listening to CDs.

Best quality is always a debatable question, but hard wire solutions are generally best. Stereos designed for iPod input should be best for quality, but not all function correctly with iPhone.

What model/year of car do you have?

It is clearly a grounding issue. I know that there is an iPod interface for most late model VWs. It attaches to the wiring harness behind your deck, and comes out as an iPod connector. I have seen it, and it is a very clean design!

G/L,

Ed

Goodmans (in the UK) were doing a ridiculously cheap CD/Radio/MP3 player with an iPod dock the other day. Might be worth shopping around for a direct connection.

Im using Monster icarcharger.
This is my second one. The first one works perfect at first, and it has the best quality when compare to other product, since it gets signal from the dock connector, which isnt limited to the amount of output like from the headphone jack. Plus, it has an aux output you connect, so its not like those radio signal or cassette tape.
After using for 2-3months, it dies.. I bought a new one, because it offers the best quality so far..
And i opened up my older one, and found out there is a broken wire in it.. so it can be fixed by soldering it...