I honestly don't see the benefit of removing the Air Silencer. I have two friends, one with a '97 V6 and a '01 V6, and both removed theirs' and saw no difference what-so-ever. From what I've been told about the Air Silencer is if it's removed it allows a lot more *HOT* air from the engine, while supposely the Silencer allows a small amount of only cold air in.
What I recommend? If you do remove it make sure you have a cold air induction system (which you can save money and build yourself) and a K&N air filter. Mustangworld.com has a very good article on how to build your own Cold Air Iduction system.
The link is
http://www.mustangworld.com/ourpics/fcar/coldair.htm
Hope that helps a little,
Michelle, loving owner of a '99 V6.