corsa sting 1997 missfire problems

[buggymadness]

wondering if anybody can help me with this problem . Poor corsa running on only two cyl ? lack or fuel? took to garage today to see if they could sort my corsa's problem out they changed the igntion pack and checked plugs which where ok so just wondering if anybody could help .

its a r reg corsa sting 1ltr sting 3 door seems to lack power from pull off but when into second gear it seems to try and fire up on all 3 cyl i presume as i feel a slight power increase and seems to run a bit smoother . when i come to a junction and try to pull away it seems to happen again so if anybody could give me some suggestions i will be trying them .