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Discussion Starter · #1 ·
This weekend I chopped off the muffler on my 1999 1500 5.3 Silverado and I drove a couple hours back home and gassed up. I was deplored when I figured out that I did 16MPG (Canadian). It usually does 19-22 MPG on the highway at a steady 120Km/h. I did place a piece of exhaust pipe to replace the muffler so It is exhausting at the tailpipe. Wasn't driving in abnormal conditions or anything. Its never done that bad before this. Is this that back pressure problem?
 

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sounds to me like a heavy right foot, paired with a smile.

generally your mpg's will go down after new exhaust...seems most people like to hear it when it's new!

as long as you didn't mess with anything upstream of the last O2 sensors you shouldn't have any issues. most people are misinformed about "back pressure".
 

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Discussion Starter · #3 ·
Talked to my mechanic friend. Said it was just a coincidence of timing that I probably got a bad batch of gas. Makes sense since i've had poor quality fuel from that station before. Thanks though.
 
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