Evo 8 idle problems

[Rob197]

Hi need a bit of help! Have a Evo 8 MR fq340 and it idles fine until I drive it hard or on full boost. If I do this the revs stay at 2000 at idle, which makes slowing down for roundabouts quite fun...
If I turn it off and wait 5ish mind it will be fine again and idle normally. ICV tested and its working although I've bought a new one just incase it's intermittent fault. Any ideas? Thanks

[PorkRind]

Pop over to the MLR where you'll get more information about the evo than on here.