yep thats the problem with mfi, fuel everywhere, unless a 5th injector is fittted of cause,

the co level i would say 3.5%, give it a rev to 3.5k revs and hold it and see what happens

i had mine lambda checked on the road, at APT, its not that expensive,around £80, compared to blowing your engine up, it will cost alot more than £80 mate