Caching

I have just implemented caching on my site using wp-cache. Overall the performance is much improved. The two pages that give me trouble are bfa_ata_file=css and bfa_ata_file=js. I removed those files from the wp-cache list so that they are not cached (I got strange css behavior otherwise). Since I can't cache the results, I want to cache them in the browser. What I have noticed is that these files are returned to the browser with a no-cache in the header. I want to change this so that they return a cache-able page. I know the point of externalizing the css was to allow the browser to cache them, but when the header says "no-cache, must-revalidate, max-age=0", it won't get cached. What php file is setting the header for requests to bfa_ata_file?