Just bought a 2004 G35 Red from a grandpa who was its owner since 2004.

Any tips or mods I should definitely consider?

 

Plenum spacer, rev-up air box, high flow cats and cat back, tune, sway bars, rear differential bushing.

This of course is all after you get it back to OEM condition, most suspensions bushings are probably about shot, front struts and rear shocks as well.

If you plan on lowering at all (and you should!) then you will also need a camber kit which is typically adjustable front upper control arms, rear camber arms, rear toe bolts. Rear radius rod is optional but recommended since it replaces the crappy oem rubber bushings.

 

^^^ and listen to this man. Post up some pics!

 

Definitely pics!