I'll leave all the 'most horsepower' stuff to those who race at Laguna Seca. My 2000 ZX-9r (
see this link)has plenty of usable power and I actually had to lean the main jets for where I live, yet they're still richer than Kawasaki recommends for operation over 4,000' --
Haynes repair manual. If I were you, I'd buy some sort of repair/shop manual and check to see what the previous owner did to hose up your carbs. I wouldn't know how he removed the reserve, that doesn't make sense. Perhaps he removed the main tank's internal fuel tube so there's only 'REServe'. The tank should be a 5.0g stock tank.
The carbs on the F appear to be similar to the E, but are not identical. Your main and pilot jets appear identical to the E1. If yours is like mine, the stock main jets should be #160/165 (outer/inner cylinders). I wouldn't be surprised if you find some wild setting like #190/195 mains, pilots greater than #40 (#38 is stock) and jet needles that are shimmed up too high.
Read my link and check out how your carbs are set.
Also take into consideration the altitude you're driving at. From what I've heard, the pilot air jets should be around 1 1/2 turns out (+/- 1/4), some go as far as 2 turns, but then I hear there are negative affects for going beyond that.
Factory Pro is a good source for tuning as well. I've seen many recommend it. I'd say they're more accredited than I. And there are plenty of examples online of properly tuned ZX-9s getting at least 45+ MPG.
Example.
I have yet to empty the tank dry. The worst I've seen using only 91 octane, prior to carb adjustments was 175 to reserve. Now (09/06/08) it's 206 (208.1 to gas station with 3.789g into fuel usage) and probably a touch higher for highway only riding. Mind you, I'm not cruising at 140MPH or riding around town in 1st gear, like most of you are (by the sound of it), but I'm not 'representing our sport' well either.
2000 ZX-9r E1 California model, double oiled K&N, Supertrapp slip-on, altered main jets, but otherwise stock.
