Update: Since i've installed the muffler, here are the average MPG results. Before the upgrade i would get 25.5-27.9 MPG. Week one (i was flooring it alot) with mixed highway and city travel i got 27.03. Week two (same mixed highway/city driving) with alot less flooring of the car (but there was a couple of times where i had to kick it into high gear) i got 28.14 MPG! I got the car to break the 28 MPG barrier! Now this week im going to try and refrain driving like a nut just to see what ill get this time around.