I know these cars not meant to be speed demons but 5 seconds not good enough for me stock, best parts I should buy or save up for to get within the 4.3-4.6 range ?

 

supercharger

https://www.stillen.com/2009-2013-in...-polished.html

 

Is that the only option this far have ?

 

It is probably the most reliable option and it is street legal.
https://www.drifted.com/g37-turbo-kit/

My own experience (not G37) with custom turbo kit is endless of head ache. Custom turbo kit tends to have more issues such as vacuum leak, tuning, oil/coolant supply, over heat heating, engine cannot handle the pressure and oil came out from every gasket....etc. The lesson I learned in a hard way is that if a car did not come with a turbo, don't put a turbo in there. You can enjoy the momentary of glory and dealing endless of drama after.

have you look at this?
https://www.z1motorsports.com/z1-pro...ge-p-7223.html

 

If you’re looking to improve by 4-7 tenths of a second, then maybe its your launch technique. What do you do to get the best time/launch ?

 

As of now just throttle control alone gets me 5 seconds, just aim to get less amount of wheel spin, that’s in regular drive mode, still practicing driving in manual mode so until I fill comfortable I don’t go into that mode, and sport I only use when I’m on highway for overtaking.

 

Weight reduction, lighter wheels with sticky tires, diff bushings and diff brace (to help put it all down). After that, open her up with full exhaust, 3in intakes, and a tune.

 

Depending on your wants you purchased the wrong car. I don't think you will see better than high 4 second 0-60. I regularly see about 5.2 on the street with street tires and 7AT with a 3.69 differential swap and tune with bolt ons