Not in Klang Valley, but there is this place in Petaling Jaya (Happy mansion). The char siew is very nice (and also the roasted chicken). It's so famous that the char siew is usually sold out by 12.30pm (sometimes even 12pm already finish). So, usually people will sms to "book" the char siew first. Price-wise, is slightly expensive I think. RM6.50 for a plate of char siew rice (can't remember how much is it for just char siew). If you want the phone number, just PM me.

I think you can easily find the location from Google maps by searching for Happy Mansion, Section 17. The shop's name is Restaurant Choon Yien. It's opposite the former 6 to 10 Grill & Nasi Lemak (shifted to Aman Suria already).