I've got one on my D2.
I got it from alive tuning, it's essentially the body of a stock GT2052 with bigger internals. Mine's also a billet compressor which is a bit lighter so spools earlier.
Real world it starts to spool at ~1500rpm so is better than stock.
Top end it's phenomenal.
But, you really do need to improve other bits of the car to get the most from it, bigger intercooler, boostbox/uprated MAP, remap. It all adds up.
No way does it result in more mpg, it's just too easy to cane it about.
Oh, forgot to add, I also fitted an Allisport uprated cast manifold. Bent the stock one, split a tubular one! Also have replaced my cylinder head because I reckon I cracked one of the exhaust ports due to high EGT. In short, stay clear if you want hassle free motoing.