Thanks to Dana67, Rat, 33Imp, Oldmanmopar, Rumblefish (Rob) and Justin for taking time to post.
It was after watching the Engine Masters cut out episode that prompted me to open up the cut outs to see how much better it would run without exhausts. My lack of knowledge meant that I never thought it would cause the engine to run lean (or lose power)
My plan now having read all of the replies is to install AFR gauges on both banks, run 42" long pipes and a pair of straight through mufflers at the end.
Looking at the Duster pictures posted by Oldmanmopar, I will probably fit an H pipe as well.
Really appreciate all your replies.
