My tuner uses Castrol Transmax Z so that's what I've stuck with, would like to try the Gulf Western stuff one day.
My BF XR6T has 320rwkw with Nizpro older style cooler, Manta 2x2.5" exhaust (twin cats), 42lb Bosch injectors (limiting factor) and intank fuel pump upgrade (Walbro GSS294 - tuner choice).
Cost me about $5300 including XCAL3 box ($600), got the injectors for $200 with some luck, exhaust $1800 (new but mild steel). The cooler and pipes were about $1200 used delivered from the East coast. The rest is tune, fuel pump and fitment of exhaust by the shop.
Looking to get some 1000CC KPM squirters installed by the time I enter Racewars in March next year and hopefully get about 350ish rwkw (see what happens as the car has 311,000km on it now).