There can be a few possibilities. You first should make sure the air cleaner assembly you installed does not have any vacuum leaks. In other words, if there were any vacuum hoses connected to the previous air box they must be properly connected to the new air box. Even a slight intake vacuum leak will cause high HC. Plus make sure nothing was disturbed while replacing the original air cleaner.
The second condition is simply having your BMW's catalytic converter not hot enough. A vehicle will never produce identical emission results during the emissions test. The temperature of the CAT has a lot to do with HC reduction. The hotter your BMW's catalytic converter during the smog test, the lower the HC; just be careful of NO. NO increases with CAT temperature. It's a fine balance.
At any rate, HC should be well below 60 ppm during the smog test. With HC amounts such as this, most definitely an emissions problem exists which will need to be diagnosed. Read the following for more HC faults.
What Causes High HC?
