gl with that, there is a reason ours are called bastard b's. personally i think the stock is fine unless you want the looks. i may be wrong and im sure if i am ill get checked on it. still gonna stick with stock though =P
A header will add a little bit of performance, as the stock manifold and downpipe are pretty restrictive. There is usually a pacesetter or obx header on ebay from time to time. Most of them fit the b20a5, but occasionally there is one for the b21. One thing to consider about the b21a1 obx though, is I've read that there may be a fitment issue. The downpipe may hang too low under the oil pan and bottom out. Supposedly the fitment of the b20a5 version is fine.
Or you could keep an eye out on craigslist for a used DC Sports header. They are not produced anymore, but there are a lot of them still out there. That's how I got mine.
Another option would be to buy a header for the b20a5, as it will bolt right on. There are some things you need to do to make it work though. You would need to plug the two 02 bungs on the header, and have a bung installed in the downpipe. The other thing you need to do is either delete the EGR if you can get away with it, or if you need to have it, get an EGR tube from a b20a5 and replace yours with that one.
I know this thread is old but yes my headers downpipe on my 1990 B21 does hang low AF. Riding on stock suspension if I park and look under the front of my car all I see is the downpipe that hangs roughly halfway between the bottom of oil pan and the street. If I were to lower the car an inch im afraid the downpipe would truly bottom out like crazy. Its already flat and scraped where it bends from hitting dips.
Anyways I just thought I'd add to this thread and maybe start a new thread on how to fix if possible.
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