ok. here is my idea of CHEAP bang for BUCK improvements of NA skylines.
1.clean your car out- Take all the Maccas rubbish and non-sense weight. cut it down. - its time to clean our your boot!
2.you loose weight!!! yeah you fat ass, go to gym and work out loose 5 or 10 kg!!! its good for your health and for the fuel usage on the Skyline
3. Keep check your oil, radiator waters, Especially TIRE PRESSUREs including your spare tires.
4. Just drive it with sense on the road, do not rev out too much or drive like you OWN a GTR!!! you dont!
5. Keep your car tidy, clean. and service it regularly
6. then you are ready to put on any bolt on upgrades... what ever you fancy.
there you go, my tip for the day
cheers
Joe