I just got a cat back exhaust done today, a one in two out flowmaster 40 mandrel bent piping and two angle cut 3 Inch tips straight out the back. It's gorgeous and sounds great. I was wondering if anyone knew what kind of Average fuel economy gain I can hopefully get.. Thanks

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2001 xlt 4x4
torsion lift
kenwood speakers/headunit
20% tint
4.0L gas drinker v6