Emission too high

Can anyone tell me how reduce the emissions for MOT, basically this is the only thing it failed on....Probably on this site somewhere but I can't find it.

My emission are about 5.232% but should be around 3.5.

Thanks in advance.

Find a better MOT station lol. Do you drive the car a lot? May need a real good thrash before it goes for its re take or check your plugs etc.

has not been driven for a while but did give it a thrashing....failed last year when I was driving it quite a bit, but I knew the mechanic...always helps! lol

I'm guessing your gtir is pre 92... Mine is 91 doesn't have cat and co is at 0.4% You might have problem with fuelling there airmass lambda air leaks etc. Does car drives ok??