Too many redirects

I'm working on a drupal CMS system with apache 2.2, drupal 5.12 or something like that, mysql on a red hat enterprise server. This is a system that runs for a major commercial website, so tons of requests going back and forth, and things need to be fast. However, on a recent zen page, my boss and I discovered that the load time was annoying, and found that one reason for it were multiple redirects, caused by using Zen in combination with Domain Access and Clean URLs. Comparing the system with Garland, I found Zen was a decent amount slower. Notably the repeated back and forth between the theme engine and the path system with redirects for each step of preprocessing for each element was wasting a decent amount of time. Now speed is quality, so I was wondering if anyone else has had this issue and if anyone else might know a solution.