I bought my 2005 S 4x4 w/auto new in 2005. It has 38K miles. It seems to shift really soft under accelleration. When I let up on it, it takes 2-3 seconds to upshift.

99% of my driving is on road. I'd love it if it chirped the tires from 1st to 2nd but I doubt it has the muscle to do it. Therefore, just a firm shift will do. Does anyone know how to get a firmer shift? Any adjustment or aftermarket equipment to do this?

To do this, you'd have to reprogram the TCM to get the line pressure duty cycle to up the pressure. The transmissions in these aren't like the 'Camaro' of old where a little shift kit with some firmer springs and a different accumulator piston would do the job.

I don't know of any company that is working with the transmission, but you might call Uprev in Texas and see if they have anything. I know they work with the 350Z, Titan, Armada and G35's, so they probably have a better clue as to what's out there.