Kuala Lumpur, Malaysia is a great place to be in. 4 days might not be enough (any number of days in any place isn't good enough for travelers, is it?) but you can do a lot in 4 days, though. If I were, I'd plan it this way ( you may, of course, do it according to your own preferences).

Day 1: Get on to the "Hop on Hop off" city tour in Malaysia. It's popular and it's also won "The best of Malaysia awards in 2009". You have a choice of 24 hrs and 48 hrs ticket, multi-lingual commentary, Wi-Fi on Board, Skyview & opendeck ( Paris style), and it covers over 40 major attractions. You just get off the bus, see places, eat, shop around, lounge in parks, and get on to any other bus you might see next when you are ready. You can take your time and it isn't rushed like most other city tours are. Now, that's awesome, isn't it? The ticket costs just RM 38, I think.

The rest of the days, you can go on themes. Like "Food", "Shopping", "Nearby getaways", etc

Day 2: Food & Shopping -- Start with Little India, China town ( Petaling Street) and other places famous for street food and other delights. You could try any or all of the food items. Malaysia has an incredible mix of South east Asian food. There are plenty of day markets, shopping malls, etc., where you could shop till you drop.

Day 3: Nearby getaways -- 2 hours to Melacca, 4 hours to Johar Baru. A flight away from Kota Kinablu. 1 hour away from PutraJaya. Just hop to a bus and head off to a nearby 'must-see' destination. It can't get better than this.

Day 4: Chill out or go partying ( if you like that). Malaysia is vibrant and tolerant. You can go freak out into the night partying like mad or just chillout. How you do it is up to you. Plenty of places on the Internet to help you plan. Try Trip Advisor for ideas.