The new cav had a few problems when I first bought it but the garage I got it from balanced the tyres for nothing (wobbly wheels) and went halves on a new water pump - it was peeing it out after 2 days of having the car.
I thought I'd found the strange petrol smell problem - the hoses on the injection system were slightly loose but after another 100 miles, the petrol smell was back with vengance.
I took it into a local garage who couldnt find anything wrong with it, took it to the local vaux garage who were also stumped (didnt charge me though).
The car was in need of a service anyway so I got some new plugs etc for it and lo and behold - the old plugs could be unscrewed by hand !!!! It must have been pushing a bit of fuel vapour out every now and again cos new plugs torqued up correctly seem to have solved the problem