I was thinking about running an hks supper dragger on a n/a 73' 240z. I have a 6 into 1 header right now with 2 1/2 exhaust pipe that runs into a muffler at the end of the exhaust. But then I read some posts and it seems everybody is running there mufflers a couple feet behind the header to create back pressure/ horse power. What are the pros and cons of each set up. What kind of probblems will I run into.