Tom, From my limited knowledge - and I'm only an enthusiastic DIY mechanic - it can only be one of two things:- 1) - not getting enough mixture. 2) - not getting exhaust out. The car runs fine, pulls reasonably well low down, but when you get to 4.5 / 5K it just runs out of puff - it will rev to 6.5K but as I've said in previous posts, it feels asthmatic doing so. It ticks over fine, it doesn't cough or hesitate when you drive it, it doesn't smoke, spark plugs correct colour...etc...all the usual checks tick. There is nothing untoward with the running of the engine until you drive it and feel how gutless it is, it sounds fine and not like a box of frogs at all. Changed oil and nothing untoward in that. Same for coolant. So I'm scratching my head. If it sounded terrible on start-up, or made a load of clanging noises when driving then at least you could say the engine was shot, but it doesn't give any clues to how feeble it is unless you boot it. During normal road driving you wouldn't tell anything was wrong with it. I want to tune it slightly anyway, and future proof it for more tuning - so if it is a completely knackered CAT in the exhaust (I don't think it is, but it will eliminate that possibility of a blocked by putting a free'er flowing exhaust on ready for the future tune). Likewise with the throttle bodies and ECU - once set up it should pull like an express train. Again, I'm no expert but I think the cam timing is way, way out (from possibly a belt change previous???) - I'm not competent enough to adjust this, but my diagnosis with how the engine physically runs and feels, it can't be opening the valves soon enough and closing them too quickly. Unless I'm on the wrong path altogether?