I do hope you mean driven by the empeg, not powered - the only supply line coming from the empeg is the 12V (blue) amp enable/antenna on line that signals when the unit is powered on. Draw too much power from this line, and POW - dead empeg.

I am unable to determine if you actually have a tuner module fitted - I am assuming so - where do you get the bad reception, AM or FM? Both? Just one? I am willing to bet you are getting poor FM and good AM. Which tuner module do you have (factory black box, or PCATS grey box)? If it's the PCATS, who built it for you?

I would be inclined to remove the aerial from the car completely, and clean up the signal connections, most importantly the signal earth. You also need to make sure that the aerial is earthed properly, via bare metal, to the bodywork of the car (not just sitting on top of paint). You need to protect the contact with a smear of Vaseline. If you have a multimeter, and the antenna is not an active (amplified) one, check the signal continuity between the centre signal pin on the cable and the antenna body (assuming it's metal).