Im not sure if my muffler is slowing my car down or making my gas millage worse, when im driving and take my foot off the gas it significantly slows down and i feel it slowing down fast, if i put it in neutral i feel the coasting feeling. It happens even when i go down hills as well.

If the muffler is the problem how would i go about fixing this problem without spending too much money??

 

It's not the muffler, it's your torque converter.