Think you could be right about it being a pulsed out put from the flow sender,

http://www.race-technology.com/conte...pcat=2&cat=728

I guess most senders will work using the same theory. Still not an impossible thing to do though mate. Ie, using a simple calibration circuit to alter the output of a sender so your fuel computer can make sense of it.

Assuming, the mfi sender is looking at 1/4 fuel used, (one injector), placing the sender on the fuel rail input would mean it was looking at 100% fuel used. So a simple circuit would divide the pulse out put by 4. Not sure how clean the out put from one of these is but if your fuel computer can interpret the results it can't be too bad. I think the pulse width will stay the same.....