Ultimate Racing High Flow catalytic converters - Great quality and fit. They sound great. If noise is of concern, these cats are the choice. The Nismo S-tune exhaust seems quieter after installation. The car starts much quieter and freeway cruising is quieter. I believe this is because the exhaust is much deeper and does not resonate in the cabin as much as before. WOT is definitely louder and more exotic, especially under high load. Rasp occurs at 5500 and up. There is a noticeable gain in mid range power. The car pulls smoothly from 3000RPM to redline.

Nismo Powersteering Cooler - its much longer than the dinky factory cooler. It installs perfectly. Could not test cooling.

Nismo rear diff heat soak - it looks cool if you can actually get low enough to notice. The synthic mobile one diff oil makes the car rear coast smoother. The diff oil is also louder than the factory Nissan fluid.

Nismo Thermostat - the car runs cooler. DUH! It works.

I would like to take a moment to mention Z Car Garage for the excellent service and workmanship. They installed all these parts with care and took time to explain each installation.