check out the search button,this has been covered a bunch of times. its pretty common question from SP1 owners. to use an SP2 system you need an SP2 header. the sp2 header has a d shape exhaust port while the SP1 has a circle. some guys worry abot this d shape messing with the circle port on sp1's but i dont think it has any noticeble effect. if you are worried about it or are as anal about it as me then use do what jondog did and cut both headers and have the sp1 cnnections onto the sp2 pipes.