Do you guys think that a high flow cat and a flowmaster muffler would make a difference in my mpg.It is for my 90 Dakota 3.9. Do you know what size pipe is on the truck factory? Where can I find a high flow for this truck?

 

2.5" factory if I remember correctly, high flow cat will help some on your mpg's, no miracles or anything, muffler won't really do much but it will sound sweet.