have you ever had it running? driven it?

if stripped down or left for long periods they can get air locks in the injector lines, theres also a non return valve that dies that allows fuel to return to the tank which also causes an air lock,
any form of air leak in a vacum, the main air hose or inlet will also cause poor starting and would also make the engine idle high

if you can make Tea i would happily pop round and have a look at it with you