Background Noise

[GoodRevs]

So I've got my X710BT working perfectly in my 2001 Lexus ES300. I'm having one final issue, and that is of background noise. It's in two stages and occurs even when audio is off. When the engine is off and the key is turned to "accessories" it's a very low level, barely audible hiss. If that was all I wouldn't mind much since you can barely hear it over the Avic's cooling fan. However, with the engine running the noise is much louder, more like a crackle. If the car is idling in park it's easy to hear, but on the highway it's barely audible over the road noise. I am using the stock speakers and amp, nothing changed other than adding the new x710bt headunit.

 

I have two ground loop isolators installed, one each for front and rear RCA outputs. I had limited car chassis around the unit so I had to fabricate a ground onto the car via a nut and screw for the ground on the cars harness, the avic's harness and the parking brake green/white wire (three grounds in total). Perhaps these ground iare what's causing the noise, but then wouldn't the noise be the same regardless of whether or not the engine is running? I'm lost here, if anyone can assist me please post up. Thanks very much.