Sorry but KL is dull for visiting. Two days is more than sufficient. I would go to Melaka or Penang, Kota Kinabalu or Kuching if I had my way. Flights are short (2 hours 30 minutes), in-expensive (Malaysia airlines or air asia) to east malaysia or a 1 hour flight to Penang.
Food in KL is hit and miss. A lot of the outlets do not employ local cooks but have foreigner workers doing the cooking so, once again, it will be hit and miss especially for local malay and indian food.
However, given Malaysia and its cultural blend of so many cultures from indian to chinese to malay, there is a lot to see but....finish what you need to see in KL and go somewhere else. 6 days in KL is very very long in my humble opinion.