is there a connection between digestion and metabolism?? does slow digestion imply slow metabolism?? how long should you stomach take to digest food on average??

There is a link between digestion and metabolism, but then every system is interlinked. It is possible to have a slow digestion and a normal metabolism, for example if your digestive system lacks a particular enzyme, has slow peristalsis, etc.

Here's a link to several articles that discuss various aspects of your question:
http://www.nlm.nih.gov/medlineplus/foodnutritionandmetabolism.html