Is it definitely a fuelling issue? Have you pulled + tested all the injectors? Have you proved good spark on all plugs? Have you tested the compression and checked the cam to crank timing, as well as inter cam timing? Do any wires or senders look grotty? Have you tested all 3 cylinder head sensors using the temp gauge if you haven't a meter? Have you got a strobe timing light so you can check the dizzy is set correct, and advancing properly? These are the fundamentals in making a 16v run good. Fuel pressure test kit (if you can beg, borrow or steal one) would be good as well to prove pumps, accumulator, wur etc.. Not meaning to throw loads at you but it pays to know all the above + more is all working tip top. You should also know the state of things like the thermo time switch, cold start injector, throttle (inc micro switch) and isv, as they all need to function correctly as well for good running, though in your case it doesn't seem to be a startup/idle problem so they're prob ok. Get to know your 16v buddy, don't sell it. Then you can reap the fruits..
