There's a reason that 90% of the fastest street cars in the world run Flowmasters and do you think that they might still be in business if they hurt performance? I have Bassani headers and one cat mid-pipe, an X-pipe and two single chamber flowmasters, all 2 1/2 inch and love em. I know some people have said that they hurt performance on the Lightning, but I find it hard to believe. And to be honest, the stock muffler is a decent muffler that comes on the L and if all that you upgrade is the cat back, don't really expect much more than a sound increase, IMO.
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