Was the engine light on prior to you fiddeling with the car ?

Running teh engine with a sensor disconnected will put the light on so you
may have caused that your self ?????

The lambda sensor doesnt affect fuelling much. It only trims it so wont
cause the engine to judder.

You can test the coil pack but a valid test wont nessecerily rule it out from
being faulty.

On the inputs you should have about 0.5 ohms on each coil.
(cheaper multimeters will read this as a short circuit )

On the coil outputs to the HT lead, you should see a high ohm reading of
around 5000 to 10000 ohms (5 to 10 kilohms)