My understanding is that "higher lift" camshafts will give slightly more BHP at the expense of torque at lower revs. So in a racetrack situation when high revs are being used, there would be a small BHP gain but for normal road use the benefit would be questionable. You may also cause a lumpier idle, higher fuel consumption and need to make other alterations to cope i.e a remap. My own opinion is that when you are using a normally aspirated car on the road, you are quite limited with the "tuning" alterations you can make other than ensuring that the car is in tip-top standard service and tune condition.
Personally (must admit I am a bit boring
) as you have the single cam 1.9 M43, I would focus on things like new top quality spark plugs, possible renewal of the HT leads (1.9 feature only), getting the injectors cleaned and new air filter.https://www.youtube.com/watch?v=WQN-0zvZNbY