We have not got any dyno numbers yet, but 8psi should add roughly 65 horsepower, and 10psi should add roughly 80hp. Could be a little more or a little less, but that's a good ballpark figure at least.
We have always warrantied our parts from fabrication defect, and if any of our parts fail we would repair them. We have been tossing around the idea of doing a limited lifetime warranty on the exhaust manifolds as well.
Its pretty straight forward to install, we made a pretty comprehensive installation manual which includes detailed instructions, photos, wiring diagrams, tips/pointers, etc. Most people install the stage 1 kit over a weekend, or over a few weekends (there is roughly 10-16 hours of work, depending on your skill set). We removed the radiator to free up some room to work, and this gave a TON of working space to install the turbo system. There was surprisingly a lot more room in the engine compartment that we originally thought.
The OE fuel components stay in place. This turbocharger system uses a sub injector, so you "T" off the fuel line and run an additional fuel line to the sub injector. There is a fuel controller, and external MAP sensor that gets installed as well, and this controls the sub injector. It also intercepts the OEM MAP sensor, and taps off the crank position sensor, and the TPS sensor.