Dusty,
Once you use a relay, everything including an EQ or other processor should be triggered by the relay also. Not the ignition, accessory or constant supply but only the remote trigger. All components should then share the same constant supply point. Same with the grounds. Then make sure the relay is correctly wired. You have the #30 workload input and the #87 workload output. Make sure to use this polarity. Then you have the #86 and 85 trigger circuit (pos. & neg.) that is tripped by the remote out lead on your source unit. The components of these two circuits must be totally isolated and cannot mix. Re-trace all these steps in your wiring. Draw out a schematic for clarity. I've never had a standard horn relay introduce the noise or pop when everything is correctly wired. PAC and similar DC fans do not introduce electrical noise. Is the voltage up to par during these tests? Different components do have different turn on/off thresholds.

David
Earmark Marine