I think all you need to know is does the vendor guarantee the numbers they publish? If not, then you have your answer about you'll actually get after spending $1,000+.
I'm getting ready to pull the trigger on one of these, but have heard mixed reviews. What are your thoughts on value/$? I have a 2.9 non-DFI engine with aftermarket exhaust system and I'm hoping I see some HP gains if I do this install.