,
This NACA duct in the side quarter window feeds air to the transmission cooler located where the stock fuel tank used to be. The hose is feeding compressed air to the cooler to remove heat soak in between runs. A pump continues to circulate the transmission fluid. Check out the cool JDM tape!
The duct leads to the cooler through the fuel pump access lid hole. The transaxle is fortified with an HKS transmission gear set that replaces first to sixth with stronger gears and shafts. 
This tank holds water that is sprayed onto the transmission cooler while the car is on track.Keeping GT-R transmissions cool and out of limp mode is always an issue and with limited airflow to the rear mounted cooler, the water spray helps. We don't think this tank was used at WTAC.
The car's interior retains a lot of stockness. This goes with the theme that the HKS car is more of a well sorted street car.The easy to take out panels are removed but most of the stock dash is present and nearly all of the interior switches and stock features are in place. This is probably so the car won't scramble itself into CANBUS hell. On modern late model cars, things like removing an antenna, door switch or the radio can cause the car to freak out.
This is because, on new cars, everything in the car communicates on a central bus and things like switches are actually nodes and digital encoders. Remove a node and who knows what will happen outside of the factory engineers!
The car has a minimalistic roll cage and a Bride racing seat and harnesses with a Nardi steering wheel. The rest is stock. Imagine all the interior panels in place and how sick it would be to drive this on the street!
The Bride seat is a carbon kevlar part with head protectors. 
The wheels are lightweight Yokohama Advan Forged GT parts by Rays in 20×10.5 with a 24 mm offset.The wheels are shod with Yokohama A005 racing slicks in 290/710R-20. These are modestly sized tires for a car of this weight and power. This means the car must be driven with a tire management strategy so as not to overheat them.
