What heads do the ST220s use? The block is definately common between the Jag and the Mondeo, but the Jag heads are machined from Mazda designed castings rather than the original Duratec 30 ones. Now the Duratec 30 was available in the Mk3 Mondeo in asthmatic form, producing just over 200bhp, or in Duratec ST form, producing 218bhp. Now I also know the Duratec ST lacked VVT of which Jag used 2 types (2 position in early longitudinal cars, X350 XJ and X200/202 S-Types; continuously variable in transverse and later longitudinal cars (X-Type, XF)).
The ST220 might well be the Mazda/Jaguar heads minus the VVT and with the hydraulic valve lifters, which I think Mazda also retained - Jaguar went for solid lifters, or Direct Acting Mechanical Buckets (DAMBs) as they termed them.
Either way, if you're adament you want a V6 based car, then the Americans were and always have been correct in saying "there's no replacement for displacement". The engine will need to come out and be gutted anyway, so you'd be much more sensible using a 3.0litre engine for the replacement. Even with the supercharger, you'll get a much nicer, happier and more flexible engine achieving your desired power output with more capacity and less boost pressure than the other way around. High boost pressures always mean trouble in the end, so the less you need to use the better, even for fundamental running issues such as waste heat generation. You'll need a bigger intercooler for a highly boosted 2.5 than you'd need for a milder 3.0.
Forgot to mention earlier - when changing from NASP to FI, the camshafts are wrong too. Valve timing requirements are very different when you're sucking air in compared to when it's blown in under pressure. It'll still work but a lot of power will be tied up in the wrong camshafts. You could make it up by just winding up the supercharger higher - but that's not a clever way to fix a basic problem.
