ARC Intercooler
 

I had been running an ARC intercooler, but it performed hardly any better than the stock setup. Since taking the car to the race track I've had issues with high temperatures even with the water injection.

I've replaced both the stock radiator and intercooler with larger upright front mount versions. On the race track I was getting intake temps over 80 deg C and engine temps over 110 deg C. With the upgrades the intake is consistantly under 40 deg C and engine temp under 100 Deg C (typically around 98 C).

There are arguments against front mount intercoolers, but I've had huge success combined with a radiator even without a vented bonnett (hood to you US types). The front mount design is relatively easy to fabricate and the radiator I have has a thicker core but is narrower so I can duct cool air around the side to the air filters.

The other trick to keeping temps down is to fill all the gaps around the radiator so that all air coming in the front gets to go through your intercooler and radiator.