the HP headers never went into production, the only produced header's are:
racingmazda: not recommended for customer service etc.
AWR: never heard a bad thing about it but you spend more
OBX Probe header: needs modification but can be had cheap enough to make it worth it.
Ractive has a header but has only made about 10 so far and they are in canada.
Essential Speed of canada has some good lookin headers
Wagner is making some headers also, a shorty that retains the first cat and Im not sure if he has a full 4-1 or 4-2-1 header yet, dependable quality and service with wagner.