1. "As yours is a reputable agency, I submit my..."
Well, ok. Glad we cleared that up. I'm praying you aren't submitting to any disreputable agencies of course, so telling me I'm in good standing somewhere (bribes were involved I'm sure) is pretty pointless. It also makes you sound like a stuffed shirt. Ditch that phrase.
2. "please review my work"
Well, no. Michiko reviews. Sarah Weinman reviews. ReviewerX reviews. I don't. I consider your work for representation. I know this seems like a petty distinction. Get over it. Words are your tools. Using them like they all mean the same thing, sorta, doesn't generate confidence.
3. "I know you're very busy"
well, sure, I guess. You aren't? Don't ever apologize for sending a query letter. Not to me. Not to any agent. Not now. Not ever. You want busy? Go hang out with a pre-school teacher.