cutting out

My car has a problem which I need help to identify the cause. When I put my foot down and really give the car some throttle it cuts the power on and off as if i was lifting and then stamping my foot on the throttle. It does this for a few seconds then cuts out.
It will start again easily but will only idle with assistant of the throttle as it won't idle on its own.
However.
It generally drives fine just out and about if i drive like my mum with only the occasional cut out. It will give the same symptoms when I drive slowly about but very less often and not so strong.
I have new leads and distributer and in line fuel filter.

Is this a Mixture Problem???
I do have a pieburg 2e2, which, I have to say, have a reputation….
Has anyone ever experienced this or do they have any ideas what is the problem

I looked inside the fuel tank, its clean and silver with very minimal rust inside.

From my understanding it might be either,
fuel pump
coil
amplifier for the coil
vacuum or mixture

Last thing is I recently fitted a 421 manifold and exhaust system does the carb need rejetting for this?????

In essence whats the cause of my problem/s??????

have a read of the 2e2 repair guide, covers pretty much everythign that can go wrong. could be the stage 2 vacuum unit isnt opening the 2nd butterfly properly, or as you say maybe an issue with the fuel pump.  loads of vac pipes on these so check em all over carefully, and make sure all fitted right as per the vac connection diagrams.

very last thing to try is the mixture, last thing you want to do is try to work around some other issue with your carby

thanks a lot for your advice im going to check it as soon as possible.

ive realised my car is most likely to behave as above either when going up a hill and/or when fuel is low.

is this fuel pressure i take it. i also noticed that in my fuel supply line there is air bubbles. would this need replacing.

could this be the only cause of the bubbles in the line if its cracked or got a hole or could the bubbles originate from elsewhere.

cheers for the help so far

yeah have a good look at yopur pipes for a hole or badly fitted clip, trouble is on mk1 the under car lines are metal and suffer from corrosion. does sound liek the pump might need changing

does the fuel line definatley need to be replaced with the same metal fuel line or could it be replaced with universal rubber pipe/tube of the same thickness

rubber pipe or plastic stuff from a mk2/3 golf would also be fine

right ive armed myself with some new fuel line and a new fuel pump. im going to attack the task on the weekend so ill keep you all posted on how it goes and whether the issue will be solved. thanks so far for advice everyone

ive put on the new pump and new fuel line and no joy.
Does my car have a pump in back around or in the tank. I think it might be called a fuel accumulator i know the later cabs have them but mine usnt a gti so i wasnt sure.
What else could it be

check your fuel filler neck chancers are its rust and the rust is clogging sender pick up. tack up the rear seats and you will find it under a round cover.

the only pump on your car is on the front of the block, as said check the sender under the carpet.  have you replaced the pump yet?

yeah the pump has been replaced and it has reduced the air bubbles in the line. this sender is the pick up for the fuel right? I have looked in there before but only to check the tank for rust. very minimal but i didnt check the pick up. there was one other part i query and that is the fuel pressure accumulator. what exactly does it do.

the sensor in the tank is only for fuel level, apart from that its basically a wire mesh filter on the end of a bit of pipe.  the accumulator is there to filter out any bubbles in the fuel, and also provide a litte fuel reserver to prevent fuel starvation issues on corners. i have seen some people who have removed this entirely without problems? you just block off the fuel return.  its free to try anyway, but check the tank and strainer first