Its got the 1SZ-FE engine. Its done 83,000ks and is a fresh japanese import.
A few questions I would like to ask
1) The engine sounds like a diseal at very low rpm when the car is moving. but it sounds perfectly fine at higher RPM. it almost sounds like detonation. How do I fix this? what is the likely cause? I know the car engine oil been changed in the car yard, but i suspect they will use cheap stuff. So I am intending to give it a good service myself with good oil and filter and air filters and sparkplugs etc etc. Another thing that comes to mind is that in Japan the minimum octane they run is 100, maybe it needs a tune for NZ petrol?
2) Just yesterday night, the rear lights set on the right hand side stop functioning (brake light, reverse, and indicator). I am sure is not the bulbs becuase when I switch the bulbs to the left side it works perfectly fine. I was fiddling around trying to find a fuse box, but could't locate it, and out of no where the lights started working again! Any ideas?
3) Its got a factory stereo.

I would like to purchase a new stereo for it. How do i do it?
Cheers in advance guys