In order to have more horse power, one of the best things to do is add a High Flow Air filter that goes inside the stock box. These filters are usually re-usable and are less restrictive than ordinary “paper” filters. They are great because the will add horsepower, do not require tuning, and can be cleaned with a special kit that is inexpensive...
Simota filter is one of best choices on the market!
After replacing the original air filter with the Simota Fileter, it really gives me the feeling that it adds 10hp more to my 323!!
The Part number for 1997 E36 323i is OB-003.