Just acquired my 2nd '06 G37. New one has auto. tranny. Seems short on torq. compared to my other G37S 6spd. What can I do to up the 'grunt' of the automatic. ps. only mod I've done so far is a set of K&N intakes.

 

First thing is to make sure that all maintenance is up to date on the car as that can have an effect on performance. This would include fluids, clean throttle bodies, spark plugs (depending on the mileage). This can often make a big difference.

If you're looking for additional modifications for power, test pipes or high flow catalytic converters really help with torque.

I have a 7 speed automatic and I have driven the six speed manual with full bolt ons and I actually find my car torquier and quicker to 100. Mind you the mods on the cars deferred slightly.

 

Beyond what drkay mentioned..

Upgrade rear differential to 3.6 of 3.9 final drive. There are direct swap pumpkins options to garner both options ('07 sport G's and '08 g37's had 3.6 .. 3.9 was found in 6MT sport convertibles). Gear swaps are also done by a few shops out there as well. Plenty of info around on the forum about it.

Can't really argue with adding mechanical advantage via the differential. There is no placebo effect, you're taking some of your top end torque and putting it to be more usable in the off the line gearing.