Fuel metering problem

Hi all and thanks for looking.
I'll start from the beginning.
The car has been sat for 19 years , when trying to start it, it wouldn't go . Fuel was being dumped into the bores as if on full throttle, so I have changed the metering head over and got it to run (kind of).
It wont tick over, really flat and wont pick up. Pops and bangs a bit too, just like it has been extremely retarded on the ignition timing . If I unclip the air box and lift the flap slightly with my finger it runs sweet as a nut. Also if I push up on the flap / plunger in time with opening the throttle I revs free as a bird .
It seems as if there is to much pressure for the vacuum to lift the flap by itself.
Do I try and play with the mixture screw?
Any suggestions ????
Many thanks
Jase

I wouldn't mess with the mixture screw yet.

I would start by looking for vacuum leaks. A good tip here is use a can of easystart, get it ticking over then spray around the joins in the air hoses etc. Normally if you find a leak the revs will pick up as the easystart enters the air intake system. There's a lot of joins and hoses on the system I'd bet after 19 years some of them are perished.

Also look at the injectors and how well they are actually working. Pop them out and run a flow test on them, make sure they are actually opening and diffusing the fuel nicely - this can affect the running more than you think.

Check the timing as well.

Mike.