I've had the shorties, almost a year now. Here's my .02:
They were supposed to be direct replacement for stock, but had a 3 bolt flange, so a little extra work was equired to install. And, I have found it impossible to get a spark plug boot to clear the header at the #5 plug without dinging the header. Even with that, I may have to remove the header to change the #5 plug. That may be a common problem with other headers, I don't know, but it seems to me that if you advertise stock replacement, I shouldn't have these little problems. Performance wise, they seem OK. Alot better than stock for sure.