never before have i seen it but in my 87 gt i hooked up a sound system and can u believe i didnt have enough ground and it used my clutch cable as a ground well after replacing everything from the flywhell back only then did i fig. it out 700 bucks later just a lil tip for all the do it urselfers out there never overlook ur ground wires
what did u ground it to. u should go right from yur amp to yur frame, as short as a run as possible. did u try to run it back to the batt?