Heat wrapping usually causes moisture, eventually it will crack. Yes it keeps the temparature down but is it really worth it, probably crack then you'll have to replace the elbow again. Why not get a good quality elbow, such as Tomei... Your flex pipe will help, so I wouldn't worry about it.
I have a stock SR Mainfold (cast iron), swain coated to keep the temparatures down, also a good quality elbow (Tomei) and a flex pipe. I'm not a big fan of these fancy Stainless tubing manifolds, so don't even give me this bull crap about good they are hehe... Plenty of guys here are using Stock SR manifolds and putting up good numbers
Steve.