yes i would upgrade your grounds - battery to chasis - chasis to engine

this should not ever induce noise into a system - but do the opposite -
try this measure the impedance from your battery - to chasis ground
now measure from amp ground to battery - the lower the number the better...

i have see great systems that can not get engine noise out of
i did this simple test and found a 10 ohm resistance in the ground (the cars factory ground was to a fender - fender bolts were loose..) i tightened bolts added a 1/0 gauge ground from battery to frame and then frame to engine block. all noise gone.
this car had been to 6 shops prior to me before i found it - it was a top isaca finisher that year....