Originally Posted by dynamix

Simple, get some drop in pistons for a very reasonable sum and then you can put a proper turbo on it rather than faffing around with 400 and wondering whether you have over-stepped the mark on power.

Life over 400 gets very exciting when you can put some proper boost through the car

If you were looking at staying at the 400 then the 321H sounds a perfect turbo for that level to have less lag than the OE turbo and fantastic top end. This will also keep it within the clutch capabilities. (my std clutch coped with 420+ lb /ft but was looking very tired when it got swapped)