There are a lot of factors that come into play to determine the power made on a setup. Exhaust pipe sizing, fuel injectors, fuel octane, boost pressure, port work, intake manifold, tune, ect ect.
It's hard to say how much that exact setup is making, but I don't see it making any less then that. It's probably somewhere in that area. Was it dyno tuned, street tuned, or does it just have a basemap? What motor is all of this on? Does the motor have stock internals? What is the mileage of the motor? Does the turbo have any shaft play or oil leaks?
These are all factors that come into play when you talk reliability.
Your mileage really shouldn't suffer much- especially with low numbers like that. Assuming you're tuned correctly you shouldn't be getting less then 25mpg driving it normally. I've heard of people running 250hp+ still getting 30's on the highway.