18 months ago the wife's 1994 306 Cabriolet started to run really rich, took it to an independant garage who replaced the Lambda sensor.All seemed well for a while. Then it started running rich again, took it back to them for MoT and they did something to sort it, not sure what. Now it's running like the choke is out (I know it hasn't got a choke) but you know what I mean. The yellow engine warning light is now on almost permanently, the car is doing about 19 to the gallon and I'm worried it's damaging the cat, cylinder bores etc. The car drives horribly, and it's smelling very sooty. The local Peugeot dealer charges labour at 70 quid an hour pls VAT, but I just don't trust them not to sell me loads of expensive parts I don't need. By the way, the place I originally took the car to have full diagnostic equipment but said there was nothing held in the memory relevant to this problem. I am reasonably mechanically minded and would be prepared to look into this myself. Where should I start? Tahnkyou for any tips. Ian.