The biggest hurdle when turbo charging the KL V6 engine is the injectors. To date the only drop in injectors that are larger then stock are the Millenia S injectors, this from the supercharged millenia Model.

The OEM KL (DE,ZE,G4) injectors are 220cc, good for about 4psi of boost, fuel pressure set to 60psi.

The OEM Millenia S Injectors are 280cc, Good for about 8psi of boost , fuel pressure set to 50psi.

Both these injectors are not an ideal size for turbo charging the KL, they will required increased fuel pressure to allow moderate amounts of boost, while they peak at 90% or higher duty cycle. The higher the duty cycle, the increased stress that's put on the injector. injectors at 90% Duty cycle can stop working or stick open, additionally at this duty cycle you're at the limitations of the boost you can run.

There are few options for Injectors that are easy, Millenia S injectors are direct drop in but don't offer ability to increase boost very much. Nissan side feed injectors are the next best option but will require fuel rail modification that can only be done with a milling machine.

Millenia S Injectors

Upgrade the Injectors
The stock KL Injectors of all KL Motors are 220cc, this is good for about 2-3lbs of boost at max. You can cheat this by raising the fuel pressure, but your limited by the fuel pressures expressed earlier.

You can find Millennia S injectors anywhere from forums to eBay, they are estimated to be 280-300cc. They range from $150 or less. If you choose to use Millennia S Injectors, you will need to change the required fuel to 10.0 in the Engine Constants in Tuner Studio.

Finding The Injectors- They look the same as the OEM blue top injectors you have now, but they will be a purple/pink top instead. They can be used in your factory rails. Millennia S injectors have been known to used up to 10psi of boost, however in most cases they are maxing out duty cycle 100% around 8-9psi boost as 55psi fuel pressure. There are other options for fuel injectors such as Rx7 Injectors, witch are direct drop in but expensive and hard to find 6. A Duty cycle of over 80% is damaging to the injectors and there is risk of the injectors staying open or not opening at all.

This is where Nissan Side feed injectors come into play, they are affordable and only require modification of the fuel rail to be used. Below is the documentation of the modifications needed. turning them into larger injectors very easily at no additional cost.