Possible injector problems

I have a 2001 jaguar stype 3.0 V6 (auto), with relatively low km's on the clock (less than 60 000km). However the car has not had its regular service intervals and now as i drive it im experiencing something odd. Either when im driving up an incline (steep or moderate) or even casual speeds the car jerks as if its running out of petrol. Then at robots while idling the minor jerking occurs again, where the car doesnt just sit at 1500rpm idle but bounces up 200-300rpm and returns to 1500 (does this repeatedly). One last observation is that even the gearbox will at times then seem slow and dim witted but if i floor the pedal (and wait 2-3seconds, the car drops down enough gears, the V6 comes to life and the engine feels perfect and strong (no jerking, just smooth). Ive replaced air filters, fuel filters, fuel pumps, gasket heads, done a full standard service (oils, fluids, brakes, etc) but still i have this issue. Could it possibly be the injectors or something more?