hi iv got a 2000 1.8 zafira which missfires ?

i have a 2000 1.8 zafira which missfires,its in the garage at the mo,had a new coil fitted as thought that was the problem.on diagnostics machine said fault 0n 1 2 3 4 cyclinder,and still no joy ,mechanic said it could be a faulty new coil???or the ecu???paid 108 for the coil and reckons 3-5 hundred for the ecu.any ideas ,thinking of giving up on her..so far spent 400 quid for no fix...only done 50,000 miles