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I'd suggest to do a compression test across all the cylinders or at least a couple to check that the no.8 cylinder is within 10-15 psi of its neighbours
if this is Ok then I'd next check the state of the fuel injector harness and injector on cylinder 8 and consider moving the injector over to another cylinder to see if the fault moves with it
if it does then you know to replace that injector with a new part
and if thats OK then it could be a lack of fuel and could be a lack of fuel pressure from the electrical pump at the tank.
1st thing to try is to remove the fuel filler cap and then flick the ignition on whilst listening for the brief ‘buzz’ of the pump
If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,Ideally measure the pressure at the injector rail (should usually be around 3Bar / 45psi +) and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.