can l change my car that has 306 hp into 500 or close without turbo or engine change.Can l add thing that will make my car fast as hell,please tell me what to add to make it fast .

It is gonna be pretty hard to make your G get 500 hp without a turbo or a supercharger but you can get some headers, cold air intake, Topspeed Pro 1 exhaust system, Kinetix SSV intake manifold and it should go way fast than now.

the g35 will not make anywhere near 500hp without turbo is or superchargers. The most you will make without turbo or supercharger is around 350 hp. Our cars come highly tuned from the factory and it is very hard to extract power from the motor unless you go forced induction. To add a little more power get a intake, plenum spacer, test pipes, exhaust, and a tune.

No the new G35 has the VQ35HR engine and its 10 times harder to tune and make power out of than VQ35de engine.
If you had the 1st gen G35 you could make 500hp But it would have to be with a Turbocharger or maybe a supercharger.
Why dont you want to turbo it.
FY l not a good idea to supercharge any VQ engine.