The car comes with 280 horse power:

2005 Red on Wheat Automatic (NON-Sport model on order)
Performance Tire & Wheel Package (18” Tires with 18” 7 spoke rims)
Sunroof
Splashguards
XM Radio
Trunk Mat

So if I add these aftermarket upgrades, where will that put my horse power?

1 K&N Filter
Z-Tube
Borla Exhaust
Stillen Grounding kit

?

probably like 10-15 more hp.

04 Black G35C 6MT | Premium | Navigation | Grounding Kit | AEM CAI | V1

actually, more like 7-12 hp heh

04 Black G35C 6MT | Premium | Navigation | Grounding Kit | AEM CAI | V1

Everyone has their own objectives, but as you consider things, my thoughts are, there is little to gain from a cat back exhaust, more from cats and possibly a y pipe.

I would start out with a z tube (for noise), cats, and plenum (for performance). See what that does for you and then decide if you want to make the car even louder with a different exhaust, with the promise of little marginal gain at that point.

<img src="https://g35driver.com/rides/spec/pix/winw_1093819995.jpg">

Wish I remember which magazine had the article on Nismo Aftermarket bolt-on products, but bottom line was that even if the products you put on your car gave you 30 hp @ the wheels, in reality due to poor gas (especialy in california) you only see about 10 hp out of the 30 hp. Now if you were to run 96 octane gas you would probably get the 30 hp.

Reason for this is becaue Nissan did such a good job getting the HP out of this engine, you need better octane to see any performance increase on aftermarket products.

2003.5 G35 Sedan White/6MT
Nismo Type S Suspension / Nismo Sway Bars
19" OZ Rims / Stillen Front/Rear Camber Kit / Z Tube
Stillen Big-Airflow Intake / Stillen Catback Exhaust

I think if you add like 2 to 3 K&N filters, you will get an additional 3-5 rwhp.

g4ian