Have a Seneca II that the right engine's fuel flow will differ by up to 2 gal/hr lower than the left. All other instrumentation looks "normal" MP can stay in sync, RPM reacts normally, temps look good. It will lag on run up, catch up at cruise with a slight difference, and really spread on deaccelerate. Have checked fuel pump pressure and it is in spec to the book. Really noticed coming out of annual, on the maintenance flight. All fuel components have been serviced (nozzles & fuel filter). What could we be missing, or has anyone run into this before?