It will be really hard to replicate our sweet and sour sauce but the basic ingredient will be vinegar,lemon juice,sugar,tomato sauce and tomato puree and water but in what measures...i don't know myself..
Just keep trying and you will come up with a good sauce plus you will need a starch of some sort to thicken it.
I am planning to go to Boston next year over the 4th July and i will surely contact you then..thank you.
You friend resturant in Boston..is it in Chinatown?I might have been in it before plus my uncle has worked in a few resturant in chinatown.
I will be looking forward to the holiday knowing that a friend is always nearby and in hand.
Take care and speak again soon.