Anything with a single, round exhaust directly in the center just looks like a big asshole. At least make it twin tipped or something! Porsche Boxter is the prime example in my mind, but not the only offender.
@Wunno Sev: Short answer is: it depends. This traded one BMW inline-6 for another. It's been done to enough E30s that it can be done well without the need for some master car surgeon. That said, I'd still give clearances, etc. a thorough look-see, and it certainly wasn't as straighforward as Honda swaps seem to be characterized.
@Turbineguy - now with reheat!!: Nah, inconspicuous tattoos scream "half-assed" to me. I say show lots of ink or don't bother getting it. (I don't have any.)
@Lotte: I was just throwing it out there. Unless they're taking off in very short order, I doubt that the prop wash from the plane in front would actually create enough of a head wind to make it a worthwhile exercise.
@Lotte: Yeah, I assume they line up like this so the prop wash from the plane in front creates a head wind that makes take-off easier for the later plane.