here is a genesis coupe 3.8. it's engine is based off the g37 engine... almost identical other than the .1 change in displacement. it has an exhaust too here's how it sounds in that same position. it comes with 4.19 gears stock. which sound do you prefer? there are axlebacks that can get the 3.7 sounding similiar to this genesis coupe if you want that high pitched wail through the revs.
The genesis coupe v6 was designed by Hyundai/Kia it shares no parts with a Infiniti or Nissan motor. The turbo 4 was a world motor developed by Mitsubishi,Chrysler, and the Korean auto groups.... I believe the key to making the sound different other than exhaust is cam profile. And as others have said ported heads and intake manifolds throttle body and full exhaust. At the end of the day there is not much exotic about the 3.7 no flat plane crank. The most exotic thing about it in my opinion is variable cam timing.
2013 3.7 MT-82:pony package,pype bomb's axleback and that's all for now
2007 4.0 T-5 :Pony package,pypes axleback, afe cold air intake, bama tuned