If he's only stuck a 150 turbo on then it won't be 250bhp; you need a bigger turbo again and larger injectors. Best you can hope for, even with a hybrid 150 turbo, is 220bhp; add bigger injectors and you may knock on the door of 240bhp. Anything above is just pub without further work
I'd get the 150 engine fixed or at least source another working 150 engine
There are sublte differences with the vac system between the engines plus a couple of other slight differences