Modify this projecthttp://themakersworkbench.com/node/399
to work with your calibration (math above)
and check here to make the program run MUCH better.http://arduino.cc/forum/index.php/topic,73782.0.html
I am working on a flow meter project also (mine uses two seeedstudio flow meters in parallel to double the flow capacity, somewhere close to 16 gpm) so that is why you'll see I have two of everything called out in the makers workbench.
If you do a search on the seeedstudio flow meter/sensor you can get some good info.