...guys you forget surge if using a std head...been there done that virtually!
You'd need a T4 minimum (and tbh youd need 2.5bar plus LOL) to make the 500bhp and at over 1.5bar you cannot get thru the surge (and my head was mildly ported)...roller bearing turbos would be even worse!.....I spose you could use a complicated jap boost controller though till 6k revs to cap the boost and then wack her up to around 2.5bar to get 500bhp maybe at 7.5K RPM?..Not sure though as std ports have real trouble accepting that amount of air.
A std engine will make 400bhp max IMO.