How to make my car accelerate faster?

I have got a focus st mk2 (2005-2012) I am a bit confused really. I no what there is mountune, dream science and blue fin but which one is the best and cheapest? Im leaning more towards mountune as I can just take it to a ford dealer to get it done but it costs £1250 which is a bit expensive for my liking. They don't really explain what it will do to my car performance wise I want 0-60 more than anything else. I don't want to make it stupid fast, what do you recommend?

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