I did that test, and it certainly helps but it doesn't make the problem go away. Would I be better to run a wire to the negative post on the battery, or try to find better grounding? also, having this wire on the sled made an improvement too. not entirely, but it did help

any input would be appreciated. the lexus forum people suck, they never post a solution. tons of people with ground loops and no "this worked for me" after everyone helps them.. makes you wonder if there are thousands of people driving around with what they consider an ignorable hum...