You need to remember when MPD first came out with the single kits, it was advertised that the 66 kit was a good replacement for the stock turbos to essentially keep stock like power with the added benefit of a cheap replacement and simple set up. If you have a healthy fuel system and trans an off the shelf turbo should be around 600hp all day long. A built turbo, billet, fmw , or decent ball bearing unit may make mid to high 600s, again, with a healthy fuel system and trans. ..... I think it's optimistic, the stock fuel system seems to be good for mid 600s.