1990 1.8 8v gti Cabriolet k-jet issuses

hey people, sorry for asking a frequently asked question.
i have only had the car a few months and i'm learning the hard way haha on purchase the car was running with a miss fire and it would struggle to fire but my heart lead my head and i bought it who hasn't? the structure of the car is sound and only has one major rust spot in the boot.
i have had it going round the block but it really struggles starting. if the engine fires up it will rev all over the place (idle control im guessing) and then stall so im also thinking its the cold start valve or the auxiliary air valve which could be faulty not allowing the right mixture into the engine.
done the usual changed leads plugs fuel filter and air filter all bosch parts from euro car parts etc. new battery (which i have killed trying to get it going) a mechanic friend of mine has helped me sort the ignition timing out.
i know the fuel is pressured up to the k-jet metering head (not sure on the actual pressure but money is tight at the moment so cant really afford to lash out on a pressure gauge but if i need to i will) which could be another problem upon why the car struggles to fire
i know i need a new filler neck from rust and im guessing a new tank will be needed also this could also be the problem as debris could of got into important areas, any one know of anywhere to get these from? found stainless steel neck and tank but looking at £400 is maybe out of my price range at the moment and im just really impatient or should i save up and get these as these will obviously last much longer.
main question really is where is a good place to start eliminating faults? im quite sure one of the 10 other owners have tampered with it and ruined it but hopefully im gonna bring it back to life
im more mechanical than electrical so i will need to do some reading up on the relay senors etc but any advice will be of great help, hoping to get under the bonnet asap now the weather is picking up again
sorry for the massive story haha, just scratching my head
thanks for reading phil from stockport
heres a pic of the engine bay anyways, as u can see not to bad considering its done 110k and 10 owners

I am no expert but have had lots of running issues over the years.  What I have come to realise is that everything you have mentioned under the bonnet, could be in perfect working order but if you have crud in the fuel tank it's only a matter of time before it starts effecting things!

I was short of money and fitted a good second hand filler neck.  Then got all the rusty crud out from the tank with a 99p telescopic magnet.  If you check thre inlet to the fuel pump, there is a small filter that should catch the big flakes.  I changed the filter under the bonnet and managed to get things flowing.

If you have a look at my old threads there is one with pictures of these things.

Thats where I would start, but also check the timing is set up correct etc

Good luck
 

yeah thats whats baffling me, could be something or nothing but i might as well start with replacing things which i know need it, gonna source new neck and see what condition the tank is in. cheers

If i was you i would firstly undo the fuel filter tank side. put the pipe into a glass jar and turn it over( but rember to pull the king lead of the ht cap or pull the +12 off the coil, you DON'T want it to start just get the pump to push fuel through )
and see what state the fuel is in, you dont need a jar full just a little will do if it has a bits floating in it or funny colour i would know  that the tank is need of a good clean out as will the rest of the  k-jet system including the  injectors that cant be cleaned. there is loads to sort but if you think that it fuel related it a good place to start.cf_emoticons__BangHead:

will give it a go at weekend and ill see what the condition is, cheers matey