You have done spark plugs and wires, right?

What you're describing doesn't sound like a fuel-related problem (power loss on 1 or 2 cylinders)

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190E's:
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black 2nd owner
http://www.maylane.demon.co.uk/190esmall.jpghttp://www.maylane.demon.co.uk/190esmall2.jpg