5le chip

Callum
Best you check about the turbo aspect, I can't see any difference between fitting a turbo and a factory one std on the vehicle.

They crack pistons quite easily if using the turbo boost above a small amount.

If you get a turbo anything then it won't use extractors at all.
Unless the engine is constipated with the current exhaust a much larger one won't do a lot. A modest increase in size may be of benefit. Many don't help much but the increase in noise satisfies some human desires. Many exhausts are overkill for size of engine. ie a 3" exhaust on V8 Landcruiser which has a effectively two 4 cylinder engines of a bit over 2 litre. No way does a 2.25L engine use 3" outflow unless it revs to around 10,000rpm.

Providing a positive airflow into the airbox will help unduction of fresh air, a snorkel may or may not improve that. Unless the intake of the snorkel enables more air pressure in the intake it is likely to slow down the intake flow pressure. At low speed there will be not much snorkel intake pressure anyway, especially driving up hills and so the idea of it is lost. AN electric switchable fan inside the intake airstream to assist intake when needed would do far more. Much modification to intake is required to use this though so fan can increase intake pressure delivery.
The DP chip may do something but unless you have sufficient air going into the engine then the additional fuel the chip provides is wasted, because it can't burn it well at all. Be very careful about overfuelling a Hilux, the resulting heat will shorten engine life if it happens.