Bit of history first:
Had a 'ticking' sound coming from the engine several months ago. Eventually diagnosed as a cracked exhaust manifold but I didn't have the money to get it replaced straight away so drove for months with it broken. Eventually I got EML and a misfire problem and it was obvious by the smell of the exhaust and the soot on the exhaust tips that it was runnig rich so took it to the garage to get the manifold replaced and a service at the same time. One of the studs on the head sheared off in the process and, short of money again, I told the garage to put the new manifold on minus one nut. Misfire still present and when the EML came back on the fault code suggested O2 sensor so I replaced both of them and general running felt improved.
Before changing the O2 sensors the engine would misfire on light acceleration or on the overrun when in low/mid revs (1500-2500 Rpm). It was a short, sharp misfire that wasn't reproduceable when off-load. After changing the sensors I have a different problem. I now get what I can only describe as a 'Splutter' that can be reproduced off-load. It seems to be more related to the speed at which you apply the throttle. Idle and light acceleration are fine, as is hard acceleration, but medium acceleration, the kind you use to accelerate away from the lights causes the splutter. It's also not entirely consistent so it happens some times but not others.
Any ideas?! dunno..