Here is what we do with 3G TL's.
1. Remove mid-muffler and weld in straight pipe.
2. Replace resonator with a Dynomax resonator (don't have part number right now).
The resulting sound is almost exactly the same as a G35/7, but this is on a J32A3 and not a J30 so I'm not sure what you'd end up with. Might be worth a try. The resonator is $30 on Amazon then your looking at about $80 in exhaust work at a shop.