Had it on mine... Oh and the back of the unit will have an earth cable (black). Check if that has remained in the loom (assuming you have the loom that runs the length of the car). If so, that's 5 metres in length and no good as an earth. You'll want to snip that close to the rear of the headunit (say 50 cms) and attach it somewhere behind the dash on bare metal to the chassis.
But try the groundloop isolator first, they're good and not too much outlay. Do a search as that's just an example of what to look for.

Not sure I can help but if close to you, welcome to help resolve.
