Looking for some advice on the best way to diagnose some intermittent sluggishness I've been having. I drive my '97 HDJ80 most days and sometimes it pulls like a train and other time is struggles a bit. I believe it might be a fuel pick up issue as I've noticed when driving up hill sometimes, it pulls very well then when flat an level again, not as well, but this is only on the odd occasion. It only seems to happen in lower rev ranges up to shifting into 5th and accelerating from 50mph which seems to be the magic number and up and around 2000rpm (could it be a turbo issue?) that I get smooth acceleration. I'm quite keen to learn from other's experience and to find the problem myself and not take it into a garage. I've recently serviced the engine, so it has had a new fuel filter. I am now going to start at the tank and the pickup to see if I need to get a new strainer on the pickup and if there is any sediment in the tank that might be hindering fuel pick up, owing to the age of the vehicle. Obviously if that doesn't help then I'll start looking at the injectors etc. I would appreciate anyone's thoughts on the matter who might have had the same/similar issue.