Took my 90 2wd Saph in for MOT and it failed on emissions on CO level

Results were CO 6.36% (3.5% Max) Hydrocarbons 516ppm (1200ppm Max)

Car is running a Colins stage 1 Chip and 1 bar boost and has new ACT and ECT sensors

What's the best way to go about solving this?
Simple CO adjustment? MAP sensor? fuel pressure/regulator?......

Cheers

Gordie