Thanks Alex 25 . That is an very interesting thread. Now that I read all those posts I think there must be some issues with some of the pcats tuners. Has anybody who posted there found a solution to the problem at all?

To answer the replies I got here:

I don't think it is the wiring, since I was using an original empeg tuner on this same car install. Before it broke for other reasons (at least that's what I think. See here if interested)
it was working great. The signal bar was not at full unless I was actually getting full signal. Now it shows the same problems that were mentioned in the thread Alex 25 is referring to. Moreover, the reception was significantly better!

Also, before using that original empeg tuner, I had another original one which I have been using for two years in my previous car. Unfortunately that tuner (I purchased it from empeg when thery were still selling them) was stolen with my car, but it used to work great as well. As a matter of fact, it seemed to me that it was even better than the one I have on my Audi now, but I think that deopends on the fact that on my old VW I had a stick.out antenna on the roof, while now I am using the rear window one. Personally, I think that tuner on my old VW had the BEST reception and signal quality I had ever had in my life. I was absolutely happy with it. The other original tuner on my Audi used to be close to it, even though not as good.

This pcats tuner sounds like a totally different device. I know it is not an that there must be something to do to fix it, but I have no clue what it could be, expecially after reading all the other posts at this regard.

Just to add few elements to this story, this pcats tuner has been used for a while by NT2000, who repeatedly said he did not like its reception. I was quite skeptical since my original empeg tuner was working fine and not showing any of the simptoms that NT2000 was describing to me (basically, poor reception). Now that I am trying it on my car, I notice the same problems, so there must be something different between my old ones and this one.

Now, I did not check the connection inside the pcats tuner, which I am planning to do asap. That's basically my only hope at this point. Also considering that, correct me if I am wrong, if the signal bar is full and the audio quality poor, it may very well means that the audio quality decreases going from the tuner to the empeg, right? I am just guessing here...

Thank you all who helped me figure this out, also!