"he said, if you send the cores it will cost 850.00 each for 650hp turbos made from stock housings"
Because each compressor housing is designed to work with a certain size wheel you can't just carve out the stock housing and put a bigger wheel in. I fell for this sales pitch before I did some research. You will not get 650hp from stock housings no matter how much you carve them out and no matter what size wheel you use. If you really want to see how good this company is, ask for the compressor maps of the modified turbos they sell. I highly doubt they have the maps to start with. If you can get the maps find a turbo site that tells you how to read them and compare a map of TECs turbo and a T3 turbo. I bet money the TEC is less effecient. You may get minimal gains in power from modified stock housings but you are not going to get over 500hp to the wheels, which seems to be the norm for turbos with larger housings.