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car has been running fine, then shuddering started. Changed the eight spark plugs, put four new ignition leads on, new supressor cap and fuel filter. Still shuddering slightly, not all the time. On the motorway its fine, seems to be when on normal roads..does it need a fuel pump? can you help me please.

You have covered most of the ignition items but the problem could well be a faulty fuel injector. You should rather take the vehicle to a mechanic to diagnose further as replacing parts at random is unnecessary and it will cost you more in the long run. Another thing to check is the engine's compression.