I've got a 1.2 '04 Punto and pretty much as the title says, it is suffering from a mad lack of power below 3000rpm. It is fine when its cold, but once it has warmed up it feels like it has a misfire.

Any ideas what the problem might be?

maybe blocked cat ?

Possibilities are almost endless. Do the old rev it up in the dark, bonnet open, look for blue flashes, trick (obviously once warmed up).

After that, if no blue flashes are evident, get the codes read. (If you can see blue flashes, get a new set of plug leads and all will be well.)

Post the codes here, not someone else's diagnosis.

Hmm good point re. the plug leads. I'll give that a try and if no joy it'll be down the garage for the codes. I'll report back

Not been using the car, so I've left this a while. Anyway, I've had a poke around and it has been using water so I pulled the oil filler out and there is a little mayo in the top, so I'm guessing a new head gasket is in order.

get a vacuum gauge on it and post up some readings before you do an off with its head

I was going to say check out my thread on the ECU unit
Knackered. I was getting same problem as you.
But when you said you have gunk in your oil
Its a totally dif problem!! Soz!

Yea, I won't be doing anything as drastic as getting the head off before I'm certain thats the problem

Thing is Dave, I was 50/50 on it and still am a bit. There is gunk in the very top bit of the filler cap but nothing when I pull the dipstick. But the car *is* using water...

It'll be loosing water from somewhere!

Better equiped garages (or FIAT) will be able to do a "coolant pressurisation test". This should pinpoint the leak and rule in/out a head gasket issue relating to the water channels (won't pick up a straight failed seal between cylinders, though).

Gunk on top of the filler cap often means nada -- especially at this time of year and/or if the car does a lot of short runs..

Yea, which is why I was saying 50/50 after seeing the filler cap gunk. But I noticed last night a moisture vapour out the back even when warmed up, worse under throttle which was leading me to think a blown gasket between a water channel and a cylinder. Or a cracked head :/

............well every car has at least a pint of water laying in the exhaust
everytime you burn a gallon of petrol, (thats why they rot from the inside out!)
so I would'nt worry about water vapour,
unless your having to fill with coolant every five mins!
like the man said, go get the tests done first and foremost.
mibbees a wee diagnostic also?