please help, car keeps cutting out :(

Hi
I wonder if anyone could give me a bit of help with figuring out what could be wrong with my car. its a 84 gti cab. it has been cutting out recently when im stuck in traffic. then when i leave i for a couple of minutes it starts up again.
Also when im in high revs the oil pressure light comes on with that annoying little buzzing sound that my stereo cant quite drown out. I took it to a mechanic who assured me that the oil pressure is fine and it might be the sensor thats doing that. He said that the rotary arm was f****d so he changed that. the leads from the coil were the wrong ones too and he snapped the coil plug trying to refit them so he replaced that too, and its still cutting out.
The exhaust was rattling about alot too and iv had it secured properly. I noticed that when it starts up again after leaving it theres a loud buzzing coming from under the car but that might just be the fan coming on im not 100% sure. The mechanic says the manifold has a small leak too but apart from that i cant think of anything else thats wrong. Does anyone have any ideas about what it could be.
cheers
p

theres a loud buzzing coming from under the car

Your fuel system is probably suffering from classic crap in the system . Pumps buzz when struggling to push fuel ………Been there done that .

Search how to clean the fuel system , its your best starting point .

nice 1 thanks ill  have a look