Portal system very slow

You need to look at the specific (overall) times for each request/response. You may find that some take much more time than others, and are perhaps also considerably larger files. Given that the portal is going to natively rewrite HTML, JavaScript, CSS, and potentially also Flash and Java, these are the requests that you should look for. Also consider that JavaScript loading is generally a blocking action, so a large js file, made slower by the portal patching engine, is going to cause the page to load more slowly.