What should the first mods I do to my g35 2006 sedan Be its got around 130,000 miles. I’m looking for any extra hp gains.

 

First correct ANY mechanical deficiencies, pay closest attention to wheel bearings, brakes, tires, struts, rear differential bushings, ball joints, compression arms, ancillary suspension bushings.

Then if AT:
-5/16 plenum spacer
-revup airbox
-hfc
-catback
-uprev tune

Else 6MT:
-5/16 plenum spacer + MREV2 lower intake
-hfc
-catback
-uprev tune

Will gain you 30-40whp depending on motor.

 

Cleric has gotten you off to a good start with his advice. I'll give you mine, spend some time reading through the site paying special attention to the stickied threads at the top of each sub-forum. You'll find threads like this one that will go a long way in answering just about any question you will ever have about your car. https://g35driver.com/forums/g35-sed...an-thread.html