Cleaning -
Engine bay
If you have a dirty engine bay use a squirty liquid product called GUNK - you can get it at halfords and any decent car shops for under £10.
its like cillit bang.
Spray on your bulk heads, under side of your bonnet etc and wipe with a cloth and you'll instaly see the dirty come away, i did it on some of the guys skylines at our S,W meet last weekend and they all went and bough it to finsh the job.
Interior -
For your dash use Autoglym bumper care, its a gel compound and gets rid of all marks, discolouration etc and unlike dash cleaner will last for weeks.
- Instant Power mod
wire your turbo diode for single stage boost

big difference for the cost of a 30cm wire.
cheers
Lee