I "think" the IAC valve is sticking

[Daved and Confused]

Hi everyone.  

I was having an issue with the idle on my 2002 x-Type Sport (the 2.5 V6 one).  Following a spark plug change I noticed that the car which usually idles at around 800 was revving itself when the car was moving (for instance if I let it coast slightly at low speeds it would rev up to about 1200 and back again.)  The EWL came on and it gave me a code of 0507  (revving higher than expected.) And after I bit of research I found that the IAC valve may be sticking.  I've taken it off and cleaned out the carbon.  Bit that's actually seemed to worsen the problem.  It's now idling at about 2000rpm dropping to about 1800 rpm after a few seconds.  

Has anyone in here had any similar experiences or any top tips on  what to try next? Any help and advice great fully received. 

Thanks in advance 

David