With the weight reduction (mine is very light) I have done, pods, free-flow exhaust, slightly over sized tires, etc, I am pretty confident I could do 14s in the quarter with 0-60s in something like 5 or 6 seconds. My 1978 should be able to exceed 100 mph (it has plenty of revs left at 85 mph).
I have an impreza; a well documented car in terms of performance, and my xs400 is definitely quicker. Last season I beat a newer nissan maxima that tried to race me off the line and he even got the jump on me. These are not slow cars, so beating one is impressive on this motorcycle even taking in to account that the driver may have been poor.
I will do more solid testing once the weather gets into the 50s (F) around here; it will probably be a few weeks.