This...factory exhaust is quiet and is good for 350 FWHP.
My car is loud...but its all overkill...I'd say get some catless Speed Daddy headers...with the stock catback it is still very quiet.
X2 on the open cone.
Also...clean your throttle body if you haven't. Free stuff rules...try flipping the dog bone mounts too so it eliminates movement...amybe something is making contact under load.