Here's a bit of advice for air injection BMW 2002 owners.
If your emission control is broken etc. you can improve your exhaust flow by removing the injector tubes in your stock manifold. You can also install headers $100 to $150 or a more reliable, sure fit, Tii manifold for about $150, or for less than $20 you can remove your manifold and after applying copious quantities of liquid wrench, remove your air injectors as well as the fitting at the front of the manifold. You can now re-install the manifold (replace the coupling bolt with a proper size metric bolt) and voila! much less back pressure You can also go one step further as I did. In this case take the manifold to a good welding shop and have the injector holes welded shut. Then using a "roto tool" etc. enlarge and polish the exhaust ports. Re-install and voila! even less back pressure.
Author: David M. Fishel