the air/fuel mixture richness is produced by changing the timing of the injector opening, and is controlled automatically by the ECU from readings it gets off the lambda sensor. no mixture screw - you're thinking mk2 there mate
you'll find pretty much any modern (ie, catalysed) car tends to p*ss water out of the pipe, which is why replacement exhaust sales have rocketed in the last 10 years
--- in place of all the carbon monoxide, nitrous oxides and hydrocarbons that used to fly out, the cat reacts them together, leaving... carbon dioxide, nitrogen, and water!
if the car is smelling of petrol, first things first:
* look in the boot and see if there's a spare can thats leaking
* check the goddamn fuel tank filler pipe and the tank itself. they rust like buggery on mk3s and its a very common problem. theres many on here who could tell a tale of having to replace it, including myself.
* check over the fuel lines, filters, accumulators etc for leaks - including all the way from the tank up to the bonnet, seeing if even the connection to the injector is ok.
CAUTION -
ALL THAT STUFF IS UNDER INSANE PRESSURE - if you plan to disconnect it or even just jiggle it to see if it's properly connected, FULLY depressurise the system first (get yourself a full written method, such as in haynes, and follow it), and wear a mask and fairly thick gloves. Petrol may not look much more than a highly combustible, volatile dessicant while sitting in a can, but put it under the sort of pressure required to operate an injector and it can quite easily pierce the skin on your hand, eyes etc
after making sure all those are ok, you can join me on my merry quest to make sure the temperature sensor, lambda sensor, etc are all ok, as i think i've got something of a fuelling problem thats proving an unrepeatable pain to test... and there's that "petrolly" smell after a trip, even though everything's sorted out ok (not to mention the rotting smell from water leaking thru the busted seal on the new door
)... hmmm.
