Emissions warning

I bought my 197 with a miltek back box. Shortly after buying the emissions warning came up so I checked on here and is a common problem which goes away after a bit. Which did a few times but now is on more than off. Which is really annoying and a bit of an issue if I choose to sell in the future.
Any ideas what I can do?
 
as jase said. decat caused this on mine after 10 start stops the light goes off and stays off for a good few thousand miles then back on same scenario annoying but its worth it. I used to have miltek cat back decat and it sounds awesome mate
 
yeah might be worth getting it on a ramp. had it serviced a month ago so should have asked then. It did use to go easier but now just wont go away. Any other options to get rid of the warning lights?
 
think you can get it reset with a diagnostic tool.
it may be a sencor that is on its way out.?