Originally Posted by dsimon
Upon further reflection, this may not be such a good idea.
I don't want to rain on your parade - and you really must see the Twin Towers - but if you had 6 hours, I'd say go for it. 4 hours? I would just relax in the airport. Note that the food in the TG/SQ lounge (I have no experience, someone else could chime in probably) will most likely be better than anything they have to offer at KUL.
You could still chance it if you make the 6:45 (immigration would have to be on your side). You'll have about 30 minutes to walk around KLCC and wolf down a plate of noodles or somethin'. Not sure about getting to KUL an hour before departure but that's your call.
BTW, I think the subway from Sentral to KLCC takes only about 10 mins (5 stops). Not sure about the frequency but since it's rush hour, it should be pretty frequent.