Isuzu Rodeo 2.5 2010 plate. Starts and runs fine for about 10 mins, pulls and revs properly. But if you then drive it really hard it starts to loose power and engine sounds rough. If you then ease off a bit the power increases but not back to normal. If you try to keep driving it hard the power gets gradually worse until the engine malfunction light comes on code 299. Changed fuel filter, egr valve, boost pressure sensor and boost pressure solenoid as that is what the error code is for but no difference. Any ideas what the fault is. Fuel pump appears to work fine but think it's got to be a fuel problem. Cheers.