I would recheck the torque with a different torque wrench, just in case your current one is out of calibration. I'd also take the wheels off and look at the studs, you might have some that are stretched and about to break. I would imagine it will be pretty obvious when you look at them.
Wouldn't a bottom mounted turbo setup basically end your wet weather driving days? The water on the streets here in Orlando gets pretty deep some days.
Personally, I would recommend a starting price of how much you have invested in the car minus labor charges and be willing to negotiate down from there. For instance, I might be interested in your car and supercharger, but the springs may hold no value to me as I intend on installing air ride...