Thanks to Focus Fanatics, I was able to determine that this header was a direct fit for the MK3, so I bit the bullet and got one installed last week. I wanted to share my experience with this header to help other folks who are thinking about installing a header.
The removal of the stock exhaust manifold is the most laborious part of this process. You're going to have to remove the windshield cowl, the underengine tray,exhaust brace, and part of the rear and passenger upper engine mounts. You have to do all this because you're going to need every inch of clearance to remove the stock exhaust manifold from the engine bay.
In my case, after unbolting the passenger UMM and RMM and lowering the engine an inch or two on a jack, I pulled the it forward while at the same time pulling out the exhaust manifold and was able to get the manifold out. So it is possible to do this as a one-man job, but would have been much easier with a buddy.
Also, I couldn't get the two O2 sensors off of the manifold while it was inside the engine bay, but still had enough clearance even with them on the manifold as it was being removed. I’ve seen other threads that mentioned that the primary O2 sensor cable is too short with the new manifold, but with the OBX header, it will be just long enough. You’ll have to remove one of the mounts for the O2 sensor cable bundle and that will allow the stock primary O2 sensor to fit.
With the OBX header, you’ll also get a bonus of weight reduction – without the heat shield and with the new header (which also loses the flex pipe mount), you’re shedding about 8 lbs.
As for sound and performance, with my Magnaflow catback and secondary cat, there is a definite increase in exhaust noise, but you can keep it subdued if you don't lay into the throttle and it doesn't drone. Performance wise, I can definitely feel it pulling more strongly, mostly in the mid and high end.
So I’m pretty happy with the header – just remember to set aside a weekend or so to get the thing installed. Lastly, here's a comparo pic of stock and OBX:
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The removal of the stock exhaust manifold is the most laborious part of this process. You're going to have to remove the windshield cowl, the underengine tray,exhaust brace, and part of the rear and passenger upper engine mounts. You have to do all this because you're going to need every inch of clearance to remove the stock exhaust manifold from the engine bay.
In my case, after unbolting the passenger UMM and RMM and lowering the engine an inch or two on a jack, I pulled the it forward while at the same time pulling out the exhaust manifold and was able to get the manifold out. So it is possible to do this as a one-man job, but would have been much easier with a buddy.
Also, I couldn't get the two O2 sensors off of the manifold while it was inside the engine bay, but still had enough clearance even with them on the manifold as it was being removed. I’ve seen other threads that mentioned that the primary O2 sensor cable is too short with the new manifold, but with the OBX header, it will be just long enough. You’ll have to remove one of the mounts for the O2 sensor cable bundle and that will allow the stock primary O2 sensor to fit.
With the OBX header, you’ll also get a bonus of weight reduction – without the heat shield and with the new header (which also loses the flex pipe mount), you’re shedding about 8 lbs.
As for sound and performance, with my Magnaflow catback and secondary cat, there is a definite increase in exhaust noise, but you can keep it subdued if you don't lay into the throttle and it doesn't drone. Performance wise, I can definitely feel it pulling more strongly, mostly in the mid and high end.
So I’m pretty happy with the header – just remember to set aside a weekend or so to get the thing installed. Lastly, here's a comparo pic of stock and OBX:
