Fiat punto 1.2 8v 2001,severe misfiring HELLLLLP?

bort this car 2mnths ago so far had 2 much probs,car was misfiring,2 cut long story short,iv changed coils,spark plugs,ECU amongst other things like new exhaust,brake pads had a service in sept now i am confused,it misfires whilst idle sumtimes quite violently,loses power,and suddenly gains power out of no were,when it drives its fine,when it stops its not,i have to steer clear of hills and ramps as there is no power to go up them and then car starts cutting out if i do then takes ages for me to get up etc let me know what you think it could be other than the stuff i have mentioned