2000 audi a4 radio reception

I have a 2000 Audi A4 that I just installed a new Sony cd player in and the radio reception is not very good.  I am using the ami antenna adapter (VW8) which is the powered one.  There is no visible antenna on the car so I am assuming it is in the window and amplified.  I have tried new radios and diffrent antenna adapters and it is the same.  I am out of ideas, so if anyone can help that would be great.  I have also tried just pluggin in a aftermarket antenna and it helps alot but I don't want to mount this on my car.

Thankyou

Did you happen to get your windows tinted at the same time?  Metallic tint will have a huge impact on reception when you have an inglass antenna.  Sony unit's seem to have good reception compared to many other brands out there, but many times the factory decks will outperform most (when it comes to reception).  If AM is not really a concern, you can also try a "hot rod" antenna.  They're great for FM when installed properly.  They're meant to go on the inside of the front glass (with no metal to get in the way), but you can usually hide them under the plastic of the dash somewhere with good results.