Well, every detail has been stated including handling time and delivery, if the ad is not been read before purchase is made then no other person should be blamed.
Its regardless wither I stated it internal or external gate, as you didn't know what they were. I'm the one whom told you what internal gate and external gates are. Doing high mount and external gate, It will be far more involving then sorting basic diagnostics. Have a look at every one whom got 350rwkws+ on a proper setup. They know they their skylines, their fabrications and modifications. I own skylines for 6 years and I've rebuilt it twice, knowing the car inside out, my car pulls 490rwkws, and I've been helping members here getting their results.
No offence, I don't think you currently has the knowledge or experiences for this sort of task. Return the G3 external gated turbo and send us your stock turbo to be high flowed. Once done have it fitted, get your car tuned, and be happy with 260 pump or 300rwkws E85 with stock driving ability.