Hi, far from expert myself trial and error .did you find anything else relating to this on line I read about component issues with poor reception.
firstly you need to confirm is your amp getting power open the rear panel and check amp.for power with a multimeter . If you see my diagram block A pin 13 this powers the aerial amp from the oem stereo. There are 2 remote wires on your unit 3 and 23 that would supply power to your amp these could be spliced to the wiring in your car that corresponds to the wire that would be connected to block A pin 13 if you catch my drift.I not too far from you if you get stuck give us a shout.