Custom Exhaust on 6.9?

[autobahnfahrer]

Hey,

I've been toying with the idea of putting a custom exhaust on my 6.9. I was thinking of a cat-back system using flowmasters (since it it a '79 and not yet smog exempt). That big-block sounds pretty mean with the stock pipes on it, and I think it would really sound great with a Flowmaster system. What concerns me is performance. I understand that all of these cars were dialed in from the factory and I don't want to screw up the back pressure and jeapordize performance, or worse!


Does anyone have any experience doing this or know the possible effects - good or bad? Thanks!