Help Golf Mk3 1994 1.6 Petrol 8v (ABU engine code) with Bosch single point Mono Motronic fuel ingection system.

Problem : Always occurs after car warmed up say 10-15mins on daily basis. When take foot of gas can feel severe engine braking. When put foot back on gas theres a second lag and then the car shoots off. Worst in low gears at low speed. At time engine stalls altogether usually on roundabout as you approach them slowing down and clutch depressed. No engine management lights show up. One other thing Ive noticed about it is that if you blip throttle it always seems to dip to 850RPM and engine almost stalls before RPM then goes back up to 1000 RPM mark.

Reading lots of threads seems like common fault is throttle body getting dirty. I have used Slick 50 fuel system cleaner and additive for fuel and it has left the throttle body spotless when you peer in from the top. Has had no effect at all. Have also had diagnostic test which showed Hall sensor fault which is part of distributor. Have replaced distributor and cap with new VW part and has had no effect. Have replaced HT leads, spark plugs and air filter NO EFFECT.

Going to try and get another diagnostic to see if there are any other faults but garages dont seem to know what problem is and worried that could end up on a wild goose chase replacing part after part. Can anybody one point to any simple checks I can carry out to eliminate some of the possible causes. Would faulty earthing cause this or relays. Could it be caused by air leaking dowstream of throttle body. Could it be the idle switch. This one deserves a permanent guide as alot of people appear to be suffering and you can waste loads of money on it.

Thanks