"Check Emission System" start to showed up after I replace my air filter with with K&N air filter on my 2008 MDX? Please advice thanks

 

Is this an oiled filter? If so, the oil may have fouled the MAF. Also double check to make sure you reconnected all vacuum/air hoses and your air box is properly seated/sealed.

PS. What motivated you to install the K&N vs a quality aftermarket like Denso or OEM? Seems like oiled K&N air filters are major trouble-makers.