Sweet and sour chicken not sticky I have been trying now for a while to make sticky sweet and sour chicken. It tastes great. But its not sticky. How do I achieve this?

I only use chicken wings for this. I make a sweet and sour sauce in a separate pan first, where I followed the recipe found on the internet. 

•3/4 cup white sugar
•1/3 cup white vinegar
•2/3 cup water
•1/4 cup soy sauce
•1 tablespoon ketchup
•2 tablespoons corn-starch

Combining all the ingredients in a small saucepan over medium heat then when well mixed I boil and stir until thickened.

I then bring the chicken to oven pan, spice with chuckny spice, add some olive oil to pan. Turn oven to 165 degrees. When chicken slightly begins to grill, I add over the sauce. And then increase heat to 180 degrees until chicken is done. 

Should I be doing something different to the sauce or chicken? Perhaps flowering the chicken? Or Thickening the sauce?
I would consider adding some soft brown sugar. The molasses content should increase the stickiness and thickness of the sauce overall. You may want to reduce the amount of white sugar to compensate.