I ran mine on 70hp for a while and had mild mpg gains but a couple weeks ago I loaded the 100hp onto my truck and have seen some real nice mpg gains(hand calculated)
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2007 2500 5.9 CTD...Smarty Jr, full straight pipe, torque tube gutted, Silencer ring MIA, leveling kit with 35/12.50 Cooper STTs(more to come as soon as i can
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