Removing cat for better mileage - good idea?

[phasmatisnox]

I have a 300D, turbocharged 617 engine. I've heard rumors about other cars that taking off the catalytic converter helps improve fuel mileage. Is this accurate? I talked to one of my car buddies about it, he said it might help. I also had someone suggest to me that I completely remove the exhaust system, muffler and all, and run straight pipes all the way back. I told the first car buddy about the straight pipes idea- he said it was no good because the engine needs backpressure. I agree. However, I completely forgot to tell him that it was a turbocharged engine. I would think that a turbo would provide great backpressure, without the muffler or cat getting in the way. What do you all think? Don't anyone get mad at me for polluting- the car will be run on SVO and biodiesel exclusively.


Cliff's notes:
What advantages would I get by removing the catalytic converter only on a turbocharged 617?
What advantages would I get by removing the stock exhaust system up to the turbo and installing full-flow pipes?