well i had mine done by kirmit
and he said that when installing mine he almost killed himself because they were a pain in the ass..
he had to replace all my top studs with bolts and put spacers in to clear the welds
he also bent the extractors up because they angled down a lot
and they weren't long enough so a connector pipe had to be welded on so they would reach the cat.
it took him, who does this sort of thing everyday, around 4 or 5 hours to do just my extractors.
so apparently not the best design
that being said they do flow a lot better and are lighter than the stock headers.
they work but its a pain to get them on apparently.