lol, do you remember PDC Blast? Saddar Blast? Many blast did happen during those two year I spend. Also those Liaqat Bagh Ulema Killing, or that CJ episode, BB Attack.. it's amazing to imagine so much happen in just two year time from Nov 2005 to Nov 2007..
I spend time in Lahore after Nov 2007 and in 5 years only 11 Episode happen for same.. Any how, don't compare Karachi with Lahore.
Karachi always get immigrates, it's isn't something new... even in 2006, there was an estimate more pashtoons than any other community in Lahore (I believe all are immigrants).. My family (Punjabis) were running to Karachi from 1975-90, till things become worst. So it isn't a new thing which happened.. Even Mahajirs who claim Karachi as their own also came from India.. those locals (Baluchi Talporis, Sindhis, others) are not even 5% of what Karachi today.. Karachi always has immigrants, but it was MQM first one who start that power struggle which become into many other violent episodes like, Punjabi Pathan Bhai Bhai, Muthida vs Haqiqi and so o on..
Edit: yeah, Lahore also has their own share of immigrants, there are pathans, baluchi, Mahajirs, saraiki Speaking, Sindhis, so many.. But due to port and business hub, most of the people prefer Karachi more than Lahore.. Still what ever Lahore got vanishes inside Lahore.. and become Lahori...
PS: I don't want to compare Lahore with Karachi, since Lahore isn't Karachi, Karachi is much bigger city then Lahore. And Last Lahore is not a topic but Karachi here...