I thought the head unit and ipod can read wav files?
You can use wav, since it's uncompressed.
I really doubt you can hear a difference between 320Kbps mp3s and uncompressed audio
If your testing is you knowing which format you're playing, then your ears/brain are playing tricks on you
The only really (scientific) way to do this
Is to do an ABX test
With A being one of the formats, B being the other, and X being one of the formats again
Then someone else plays the songs for you (so you don't know which format is playing, meaning the only way to find out is using your ears)
And you write down which one you think is better
Do this about 10 times
If you consistently pick the uncompressed sample, then you are right
I'd put $20 that you won't be able to pick the uncompressed sample
This test has been done countless times, 320 is good enough that our ears can't tell the difference. That's not my opinion, that's been proven
Not being an asshole, just stating facts