Problem since fixing cracked header

My 97 528I has always been a cold starter. I recently changed the bank2 pre cat O2 sensor and when doing so exposed and reopened a previously repaired crack in the rear header. Well, I fixed that amd now the cold start issue has gotten worse. When I start the car for the first time of the day it sputters really bad. Ive just gotten to where I "goose" the gas a couple quick times as Im stadting it and it levels out . Then I back out the driveway, put it in drive and it sputters again till I give a good press on the gas pedal, but then Im off and good for the day. Any thoughts ? Possible clogged cat or ccv ? I also have a little oil leak that seems to be coming from behind and a little below the oil filter area. Could it maybe be vanos ??? Im new to the BMW's so please forgive and bare with me if tthese are dumb questions. Thanks !