Would this cause my starting/running problems
 

Bosch 028142001
Over run cut off valve...?

starts then cuts out 2-3 seconds

XR3i 1988 MFi getting fuel to injectors pipes on top of metering head and on warm up regulator, nort checked cold start valve but assume so as it starts then stalls

Check the big hose/pipe from metering head to the throttle body. Splits in this will put the fueling out.

Fault:
ignition on- 2 second pump primes, FUEL is present at metering head, fuel warm up and injector pipe on metering head (pic below)
As soon as it starts 2 seconds cuts out stalls....

The car ran before but ran rich and idle was a bit high and never dropped after the engine warmed up, BUT it did not have a Fuel Pump Relay see below

Things if done to the car since buying it in October:

New plugs/HT leads
New coil
K&N air filter
oil and filter change
injector cleaner in tank
2 replacement Fuel Pump Relays Purchased 1 original purple & 1 new Lucas, Have tried both of them as previous owner did not have one fitted he had Ignition live going to relay holder to constantly run pump and could hear the pump a little noisy.
Have cleaned the air sensing plate or whatever its called that sits with the fuel metering see pic

Any help most appreciated or is there anybody in kent that specialises in K-Jectronic fuel injection system

If you want to take it out the equation, then simply pull off the small vac pipe and block it (leave the other end on the inlet manifold). This will remove it as a potential air leak as a temporary test

Right I give that a go mate eliminates another part, getting as long as me arm parts/wires and cleaning of bits just to get it to run
AAaaarrrgghhhh......

It sounds like fuel pump relay to me but you have changed it twice. My next thought would be to check the wiring to the fpr as I don't think it's getting a signal when the engine is running. It gets a feed from ignition directly when cranking but then should send signal via coil low tension I think that keeps the FPR energised.