dude, sounds like a lazy mechanic. you just gotta find someone with some real skillz.
i took my sc to 4 shops trying to track down a noise it was making, i finally took it to this one shop and dropped it off, and they called me back like 20 minutes later and their tech guy found it in under 5 minutes!!!

the other shops told me to live with it till whatever is making the sound breaks. can you believe the nerve of some of these people.

sounds like your problem is in the trunk area. theres not much stuff back there. STart with replacing the tail light harnesses. they are cheap. check the wiring for your speakers, cd changer, and amp. the check the fuel tank wires. check something. good luck

 

What kind of exhaust do you have??

 

I have the Blitz Nur Spec R, single exit, 114mm tip, all the way from downpipe to muffler straightpipe, silencer removed .

 

Your mechanic is a idiot, No respectable automotive technician would tell you to get rid of your car. Thats just dumb, no matter what your driving. There truely is a difference between a mechanic and a "technician".