I own a 97 Discovery 1 3.9 which due to (my) poor health and COVID hasn't been driven much lately. When I do drive it after 5 - 10km's it starts losing power due to fuel starvation. This gets worse the more it's driven. It' won't go over around 40kph and its sudden cutting of fuel to the engine. I've had the fuel lines flushed out, fresh fuel and additive added but the problems still there. Any advice on how to solve this would be gratefully received.