hello, have an annoying running problem that developed a few weeks ago.. Basically 1st and second accelerate ok but 3rd, 4th, 5th and 6th seem to have a stuttering/juddering under full throttle (almost like the power is being turned off and on very quickly) from the lower end of the rpm range which becomes most apparant around 4krpm. Once up towards the higher revs it accelerates normally (less load i guess), however after changing the maf it is running better and starting better but the 'stuttering' is still there.. I suspect a possible boost/vacuum leak as I can hear a faint hissing from around the alternator side of the inlet manifold and I guess this would be at its worst under heavy load.. does anyone recognises the symptoms and can give me some pointers ? cheers !