I think the bigport cams could be a goer... by them selves they might no make a huge difference.
But if you add those cams, a decent cold air intake system, set of extractors and a decent exhaust.
Give it a good service, run on Premium fuel and get the timing set.
I'm sure all of that together would make the car "feel" faster and snappier to drive. Its not one thing that makes huge power, it a mixture of small things that can make a car feel nice to drive and not a real pig.
i find a 32/36 on a bog stock 4k is rubbish, too big. too boggy, uses more fuel ect.
Match that with a nice cam, extractors some head work and a good strong spark and the little 4k will feel a whole lot more snappier and quicker.