Matt - A super job, fine detailing, masking and spraying of clear parts as good as it gets. I can't think of anything I'd add to it, I build clean like new, weathering just doesn't seem appealing to me, plus I don't have the talent for that feature as some have. Exhaust stains are as much as I do, I agree that does give a bit more realism in many cases.
You turned out a very nice job of it, great to see, thanks for posting.
Patrick