How much loss for rear mount turbo?

according to these guys turbo lag for rear mounted hair dryers is a myth. I remember watching them do a camaro on TV with the STS kit...
YouTube - STS Rear Mount Turbo Lag Demonstration

YouTube - STS Turbo Corvette on 2 Guys Garage

Thats fairly impressive and I have heard on a street car that the response is good. I dont consider that response in the video to be a "myth" Even though it reaches zero instantly (which is true on all engines when you open the throttle) it takes it a few seconds to reach its max boost. Also one thing to note is that a Camaro of that vintage makes 275 hp and is using a small turbo which helps with lag. If you are going to go through all the trouble of turbo charging you might as well make some power, which will take a bigger turbo which will make lag time longer. One other note is that the Camaro in the video is a street car and all the lag demonstrations are on the freeway where the car is under power and has quite a bit of RPM already. When you are trying to launch a car on boost it is very tough to build boost against the torque converter at low RPM. My point is still the same I made earlier and people can skew a demonstration to show whatever result they want you to see, especially a video on the internet. Just my two cents for you to consider.