I would also stay with your straight pipe. I have a 4" from the turbo back and would not have it any other way. The only two things that I have done to my truck since I got it new in 05 was the exhaust and a K&N cold air intake. I am now getting between 17.6 and 18.2 MPG overall city/hwy. I have learned to deal with the little extra noise for the price at the pump.
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