starting problem, very load and strong petrol smell ???

I have a renualt megane 1.6 VVT 2005, 5 door
but when cold the car starts first time but then cuts out staright away but if i use the gas the car really struggles to stay alive and it gives out a very strong smell of petrol but after 10 seconds it is fine, if i just keep staring it without any Gas it will start on the 3rdm time. i had put on a fault reader and it said 0010 which was cam sensor so i changed but still same problem also the car is very loud when driving it sounds like it has a sports filter, there is no holes in the exuast or any air leaks that i can see i have cheacked the coils but they seem fine but once started it runs fine aparts from the load noise like being in some boy racers vauxhall nova also a mechanic reakons it has a small missfire when idleing... please help
Thanks Jason
p.s the clucth is rubbish anyone got the same problem