Spaming the 6 thread lately, somehow i still missed this thread...
i know a bunch of MS3 guys use the OBX manifold and i havent seen a complaint yet. From what i have seen they end up pretty happy with the performance.
As for longevity not sure, but a few guys say OBX used to be pretty similar to Ebay knockoffs, but have increased their product quality in the last few years... not sure if this extends to only 2nd gen mazda parts or if it was back during 1st gen parts. So for the price, its not that big of a gamble. Either way, there are a few forums via google that have more user comments about them. Hope this helps if you happen to read this.
