Cold Starting Problems

Have a 93 Dakota auto 3.9L V6, i am having proplems starting it when it is cold. New cap and rotor, new plugs. after i start it and shut it off an start it again it is fine it just takes an extra 5-15 seconds to start when it is cold. alson i want to know if it will hurt my engine if i have only a resinator in my exause and remove the muffler. Lots of people say the engine needs back pressure, others say that you want your exaust to flow as free as possible. Can anyone help on my 2 issues????