Check all the connections on the amp and on the head unit.
Unplug the connectors and check the pins. Check the antenna connection both on the head unit and under the hood.
I believe someone cleaned the connections on the antenna from all the gunk and it was a huge improvement. I'll see if I can find that thread again.
94 ZJ Laredo. 5.2 Crate engine. 6in JKS SA Lift. 33in Destination MTs. ARB Front Bumper.