I've recently purchased my 2012 G37x about 4 weeks ago. According to the CarFax this was a 1 owner car and has not been in any accidents. It had 112K miles on it. Since getting the car, I've been going through it and "fixing" a few things. Just things so that I have a baseline for maintenance and whatnot. Here is what have done:

1. Replaced rotors and pads all the way around. (Needed to be done though the dealer threw new pads on it, the rotors were warped and causing pulsing when breaking, I'm thinking they tried turning the rotors one to many times.)
2. Drained transmission and replaced fluid.
3. Dropped the transmission pan and wiped that down pretty good.
4. Replaced P/S pump because the pully was jacked up and it was eating up the edge of the drive belt.
5. Replaced spark plugs... Tried AutoLite plugs because they were cheap. IDK why but car was running way rough and sounded like i had a custom exhaust on the thing. Replaced with Denso plugs and after a bit of driving the problem went away (of course after going through all the reset procedures). Grrrr.
6. Cleaned throttle bodies. <-- this was an ordeal too because the problems from replacing the spark plugs. YEAH i learned in the process that the throttle bodies really aren't throttle bodies. They do serve as a choke and a failsafe in case the VVEL fails.
7. New tires, Continental Extreme Contact DWS06.
8. Added in channel wind deflectors on all the windows. Love this because i can leave windows cracked open in the summer to keep heat down on the interior.

That's about it.

I am experiencing a bit of a problem that is a little frustrating and if someone could point me in a direction, such as posts or solutions, I would be most appreciative.

The problem is when the car is cold, it doesn't seem to downshift all the way when coming to a stop, and almost feels like it hangs between 2nd and 1st soo when you press the accelerator it doesn't go and slams into gear if you don't let off the accelerator. It even caused the tires to "chirp" once. Once the transmission warms up all the way the problem almost never happens.

Thank you in advance.