Lucky i was really panicking to get front springs when mine failed, pulled some strings collect 18 miles away in 1/2hr from a Mitsubishi dealer!
Fitted overnight and repaired other stuff by early Sat morning next day, phoned up and refused to fit it in until a further 6 days time, meaning they would charge another £40.
No buts, car needed daily no alternative method.
Any way your sorted now, i was going to offer rear springs, sick of seeing them and in the way together with front and rear shocks.
Could be a few things on the emissions and was thinking the same as Matt. For starters clean the throttle body out, its a good start carb cleaner or something especially if it gunged up, remove and clean.