Stange noise from engine

Hi

I drive an Octavia 1.6 Petrol 2001 Ambente, I have a few issues which may be related:

1. On start-up from a cold engine the engine splutters allot unless given extra revs, once driven for a few minutes all is fine.

2. Once in a while the engine will not start unless I give the engine revs.

3. From start-up, and also giving the car revs to go up the gears, there is a strange noise from the engine, sounds like the exhaust but when idle all is fine.

4. Fuel consumption is up, which again makes me think the exhaust but again when the engine is idle the exhaust is fine. I have to fully confirm that fuel consumption is up.

Any hints would be helpfully.