Had a flowmaster exhaust, 4", and now took the muffler off and put straight pipe in place of it. Good idea or bad and how much mileage increase can I expect. Have a 98.5 24V with new injector pump, in tank pump, superchips, just got it all back together. Oh, 5 spd also with 3.55 gears. This is in a 1 ton dually. I used to get 18 hwy with it before the pump went out and I added the superchips and also the straight thru exhaust. Any guesses on mileage?

 

About the same as you used to get would be my guess.

 

That's what I was thinking. It shouldn't get any worse than before. $.02

 

Well straight piped I will guess 15 or 16 until the newness of the new sound wears off then it will go back to about 18
Bulldog

 

Your probably right, after the newness wears off the mileage will improve. I just checked my last tank before I switched the muffler out. I got 16 mpg. I dont think that was bad considering I got into it about 5 times that tank just to see the smoke. LOL