You need either shorty replacement headers, which will work with your existing parts. Or else you will need the corrosponding H-pipe for the longtubes. With longtubes, you really want headers and an H-pipe from the same manufacturer. With shortys it really doesn't matter.

As meangreen already stated, if you are going long tube, you need to get the correct mid pipe. Staying with the same brand is the safest way and usually cheapest.