Hi EnzoMC
It is a while ago now (December 2010) since I had the Lambda sensors and carbon cannister changed on my 2006 QP. The prices then for original Maserati parts were:- Two Front Lambda sensors (£104.50 each) = £209 plus VAT Two rear Lambda sensors (£52.40 each) = £104.80 plus VAT. Carbon cannister £154.50 plus VAT. Total cost of parts including VAT @ 17.5% (as it was then) = £550.25. I took advice and delayed changing the Lambda sensors until reaching the requisite mileage rather than relying upon the time factor alone. This maintenance was carried out as part of a 43,500 mile service so I cannot give an accurate estimate of the labour charges for the work described in isolation. However, you can be certain that it shouldn't cost anything like the £1500 you have been quoted.
Regards,
Paul