the current group buy for the piper 4-1 exhaust manifold is a good deal, £300 delivered
they are also doing a downpipe and sports cat at a heavily reduced price if you buy the manifold
fit a balancer delete kit or modify them yourself, lightened flywheel is also a good mod
most leave the standard cams in place, they are fine for a stage 2 sc conversion
after 250 bhp is best to start thinking about steel rods, the eagle set is about £200 from the states and come well recomended 🙂