I bought a 2011 cummins 4x4 and it already had h&s mini max and dpf delete 4" straight pipe. It only got about 15 mpg. I installed s&b cold air intake, sinister egr delete and 5" straight pipe w/ flow through muffler. My mpg went DOWN 1mpg!?!
What could be the issue? I'm stumped! I have triple checked the muffler and it is positioned correctly.
Also I am getting a huge delay in throttle response that started before the recent mods.
Thanks for your input!!!