The Shanghai restaurant at the Mariott hotel in KL serves top grade XLB, very fine skin and tasty soup filling. In my opinion, their XLB beats the much talked about Din Tai Fung in Shanghai and many others in HK/ Spore. It only comes in the usual pork variety though, so, i can't compare it to Jia Jia Tang Pau in Shanghai where they have crab & pork XLB.
Other good dishes at Shanghai, Mariott: cheung fun with crispy duck filling (don't think this is shanghainese but it's really delicious), stir fried flour skin with dried scallop and mushrooms, vegetarian goose, chicken pie with walnut with dry tong yuen (lai sar tong yuen) and malay sponge cake for dessert. They also do lion heads, chilled tofu strips, drunken chicken and good soups, etc.
Was tempted to post in on the China board as a cross country challenge to find the best XLB in the Asia.