Welcome bloke.
the pinni is a r31 im guessing? Cant argue if its free
I hope you have replaced the battery already. My suggestions:
1 - check the air filter, see if its full of garbage? Try running for a bit without a filter (not driving around though). Could also be a fuel supply problem.
2 - Pod filter, exhaust, extractors are cheapest, could try a home made cold air intake
3 - If u have some coin or a donor enine lying around then it could be a good option
If it is a r31, try the r31skylineclub.com , despite the name, caters for r31 pintaras also - many helpful people there, aslong as you dont step on anyones toes (like anywhere i spose).
BB