Ive got this turbo its a holset hx55 with 25cm backhousing good for 700-1000hp came off a guys v8 audi 4.7l that made 811hp and spooled up ok on his . Was looking to use it on a 2jz but getting mixed reviews mainly that will be far to big and have far too much lag that will be dead to drive, was also told people using it on 2.5l bmw with that size housing no problem anyone any experience with these turbos just to make up my mind on what to do? {}
That size turbo will barely be turning on a 6 pot engine. Basically you need to be looking at the HX35 or a little bigger if you're aiming around the 1000hp mark. Not to mention the packaging issues of fitting a mahoosive turbo
Rear housing is a waste of time at that size, if you would have searched you would have come across a very detailed build thread from a guy called robinpipers who put a Holset with a large rear housing (not as big as 25cm but close) on a 1JZ in a Lexus IS220 and had big issues with a lot of lag. Getting a replacement rear housing will be tricky but measure the housings flange to the turbo core and the turbine wheel and do some searching (on here and Googel). 14 to 18cm would be about right for a 2jz depending on power goals
Pretty sure there's a guy who fitted a 25cm hx55 on his 2J Soarer, its a beast but i dare say it would need to be forged with a raised rpm to make good use of it though dude