get yourself a pod, a set of extractors, a 2.5' exhaust, and that should see it running better, and will take heaps of flogging provided its not in shit condition. then you can bolt on VLT gear, out in a vlt motor, put in a rb20, 25, or 26, or 25 heads on the 3l block, CA if its a pinny (engine xmember), plenty of potential in these cars, which is great seeing the purchase price is about the same as a set of chromies.
and there are some insanely clean r31 engine bays out there too..
i have literally hundereds of pics of r31s
wait for DVS JET to post his engine bay