I skimmed through all the links and did not see this suggestion. Someone once said that they had to resort to a FM signal booster for the tuner to work as well as he thought it should.
I will also confirm that I’ve tried all the other suggestions and I only noticed a slight change. Things like going under overpasses and between large buildings still make the signal fade out on me. I’d have to say that my current factory radio still sounds better than the tuner for my Empeg.

On the other hand I’d have to say that my “ear” for sound quality has changed since getting my Empeg and FM just doesn’t have that digital quality that I’m used to.

I have not tried the FM booster myself, but I most likely will once I get around to installing my Empeg into my new car. I'll have to see how well the antenna is.