TROUBLE STARTING & RUNNING- HELP PLEASE

Hi all. Sorry this is a long one but I am slowly loosing the will to live & keep having to walk places.
Just bought a 1982 1800 GTI that has had a turbo conversion some time ago. Car starts, just about, then cuts out if you hit the throttle. After a minute or so it will idle but almost cut out if you try & accelerate. The last owner has replaced the filler neck & cleaned out the tank. He has also replaced the fuel pump with one from a Saab 900 Turbo, new injectors (apart from 5th), new plugs, leads, cap & rotor. I have taken out the sender to check if there is any further debris in the tank & all seems clear. I got out the Haynes manual & ran throught the various tests. The pump test showed it was putting out the correct amount of flow over 30 seconds- does this eliminate the accumulator also? I cant get the cold start injector to do anything but do have power & fuel to it. I have also got a 2nd hand injector from the scrapper & tried that. It was the same. The same scrapper told me the aux air valve should be shut when cold (like the 2nd hand one he supplied me) but Haynes say it should be open. I can only see a tiny bit of light through it & if levered with a screwdriver it can be opened further.
Thanks for your time to read this & I appreciate any responses.