My car (series 1 rs running EFI) sounds like a subaru at the moment, slight hesitation when driving and idles at 1000rpm then shoots to 2000rpm and doesnt come down.

i changed the spark plugs and leads today but still the same.
should i change the coil pack?

car runs well, boosts ok......all was fine before it was taken for an mot, then it came back like this.