I mentioned this thread to Stuart at Krazy Horse today and his advice is that the big bore kit itself doesn't make much difference, however it does allow fittment of S&S gasflowed and big valve heads which do.
It's not as big a performace step as stage 1 v stock or S2 v S1 and is reletively expensive. But if you want to go beyond Stage 2 Big bore and heads is the way to go.
He's happy to talk if anyone wants too - but persevere in trying to get through as they are pretty busy at the momnet.
