TT pump with Z1's 675rs turbos, 850cc inj., doolz intake, full exhaust, ash ecu w/dual boot eprom, water/alchohol injection, bottom engine built and debating heads now. So I'm trying to guesstimate what I'll need for fuel delivery and hp level after fine tune.
Best way to tell is to have the car professionally "Tuned" on a dyno. It took a full day to dial in the fuel map on our 240 for optimum results. We ran dual walbro with -8 fuel lines and rail with 96# injectors for an output of around 500 HP to the crank at only 18psi of boost. This car sucks down so much fuel it deserves its own refinery. BUT its needed to keep the car from leaning out. I would find a good tuner and give that person the cars specs for a starting point.
You don't need to fly Ash out to do your tune. There are many tuners around the country that can do as good or better then Ash. It's easier if you live around a large city, but you'd be surprised at what's out there. Call around and get referrals. Find a tuner that has had experience with your engine type and control system. Most reputable dyno shops will have a list of tuners that they will recommend.
The best way to tell if you're fuel requirements are being met is with a dyno and a wide Band A/F meter. A fuel pressure gauge will also tell you if your fuel pump is able to keep up during high load points and if you're staying in regulation at idle. An EGT gauge is a plus for tuning ignition timing. The stock TT fuel pump should be good to just over 650hp.
I know russel is running two STOCK TT fuel pumps in his car. I have a Fuel Pressure regulator on my '92 NA, its the NISMO version. It has come in handy dialing in the A/F ratio. But what MaxDOC is saying is true. To get a true idea of how much fuel is needed, you need to have a few dyno session to get the basic idea. Then if you see that you are maxing out the fuel pump. Then you know you need to go home, adjust your setup, and then return to the dyno.