Frankly, if your query needs work, agents aren't going to give you feedback about revising it. They just don't have time for that--it's part of the writer's "job" to learn how to write a good query, a good synopsis, etc., as well as a good manuscript.
An agent who requests a partial or full of your manuscript and then rejects that material might, just might, give you a line of feedback (like "pacing seemed off"), but that's if you've made it past the query stage...and even partials and fulls can sometimes just get a form R.
So you could query 100 agents and still not get feedback on your query if it's a bad query...just a form R.
The good news is that there are lots of other resources, online and off, for query writing!
Have you tried the Query Letter Hell (QLH) thread here at AW? If you have at least 50 posts, you can log into QLH and post your query for feedback from other AWs.
You can also take a look at agent blogs like
www.pubrants.blogspot.com and
http://jetreidliterary.blogspot.com/ for tips on how to improve your query. Those agent blogs and this link to some posts from former agent Nathan Bransford's blog
http://blog.nathanbransford.com/search/label/Anatomy of a Good Query Letter also show off some successful queries to model.
Best of luck!!