Are there any over-the-range microwave units with good exhausting capabilities?

Most conventional micro-hoods operate at about 300 cfm (cubic feet per minute). Frigidaire has two models that run 350 cfm on high: the premier series and the professional series. But hold on to your hat because Kenmore has one that might take off! Kenmore Elite has a 600 cfm fan. And the Kenmore Ultra has a 400 cfm fan. Another word of caution: you might want to investigate your current system to be sure that you don’t have a bent pipe, too long of a run, or too many elbows. Any of these conditions will hinder your fan’s performance.