1996 Volkswagen Polo cold start problems

1996/7 polo 1 litre fuel injected, to start this car from cold requires full throttle & much cranking when cold. It's had new plugs, leads, distributer cap, rotor, oil & air + oil filters. It's like it's suffering fuel starvation on start up, but it's running rich when hot (probably due to loose exhaust manifold, which shouldn't affect cold starting). Going to try new fuel filter next. It starts ok (not the best) when hot, could this be a fuel pressure regulator???