25lb Turbo "How Much HP Gain?"

[Takedown]

I found a promising turbo, wastegate and oil line kit- http://cgi.ebay.com/ebaymotors/Parts...1%7C240%3A1318

I was wondering that if a stock 87 supra without a turbo has 202hp with a straight 6 cyl 3.0L how much of a power increase would I see if the turbo was tuned properly. Keep in mind I would be upgrading the header gasket and whatever else would need to be upgraded/tuned to get this to work. I will also be getting a blow off valve.

I want to know this to see if its really worth it.