Problems encouraging caching on the browser

We are still having trouble removing the Vary header via an iRule. I tried deleting it and then reinserting just what I want:

 

 

Vary: User-Agent

 

 

However, it doesn't seem to want to alter the header. In the meantime, we have removed compression, which in turn, removes the Vary header and the files are now being cached in IE.

 

 

Please let us know if there is any other specific syntac I can use in my iRule to kill the Vary header from these large files. Thanks!