My experience was similar to Marty's when I first got mine, although my mpg's did not start out as low.
Was a lil embarrassing early on in my ownership when being sporty while merging into traffic but made merging easy because the second time you looked in the side mirror there was always a hole to merge into...
I've recently done DV seals and run 4 cans of DP through and now I have difficulty getting any smoke at WOT which I miss as it was a wonderful deterrent to tailgaters.