Your aim should be to get about 2ozs in approx 25 secs. How long are your pours currently taking?
Sounds like theyre too quick and that would be because the beans arent ground fine enough or arent tamped firmly and evenly or the basket isnt full enough
Im sure you would have noticed in your forum research that the grinder is critical to good results especially with machines in the Silvia class and above.
Your roasters idea of what a good grind is may not suit silvia at all. It sounds like your beans need to be ground finer.
this info in more detail is all over the web.
(ps sorry for any typos, I cant proof the above as im running blind without glasses :()