chipping my landcruiser

I have a 4.5 litre landcruiser and it's running really rich

Now it's an austraian import so has no cat convertors on it and also no lambda sensors
It's a 1999 landcruiser 105 series 4.5litre automatic

It's doing circa 10 mpg round town
These things do run rich as standard but how would i lean it out
Emmisions at mot yestaerday was 3.4% co and 998 ppm HC

Could it be chipped to lean it out ?
Or any other sugestions

I wouldnt of thought an out of the box chip will make it lean out to much as its set in safe parameters so to speak ... maybe a  tuneable daughterboard perhaps ...