1997 1.6 SLX - Serious power loss without warning - car judders. Problem started after exhaust changed Feb 2003 and has got worse over the last few months. Car serviced regularly - plugs and filters changed, and diagnostic check results not showing any specific probs. Thought it might have been petrol blockage, but after putting 3 lots of petrol cleaner through, still no better. It's worrying driving on motorway when power drops especially when accelleration is needed. Can anyone offer any advice??

Thanks