First how many VUs do you have, increasing them should do the trick but also try to distribute the load across several agent machines if you have not. The only thing I can think of to lessen the trnsactions\sec would be to so lessen any think times. I believe that you will always have the same trans per sec because this is based on the calculation of how long the script takes to run in the base line (if the script takes X to complete you can do Y trnsactions/sec).
But in the end doesn't it all come down to BEER? Beer is the ultimate answer to all questions in the universe so yes the answer to your question is BEER.