I actually get a little better gas mileage with the Mazdaspeed CAI (the same item as the AEM) . Your engine is breathing better and more efficient. And on a Renesis engine you do get about 1 horsepower increase for every 10 degrees cooler intake charge, varying slightly with your starting ambient temp. Racing Beat and Pettit Racing have both done testing on this matter.

 

Never had any issues with my MS intake. I drove it in the winter, and did automatic car washes once a week.