After changing the oil, oil filter, air filter, transmission fluid, and transmission fluid filter my 2000 subaru legacy GT seems to be a lot louder. It sounds like l purposely put an exhaust system to make it louder. Does anyone know if by doing any of the above l could have made the car louder? l want it to be normal again.

the oil you put in may have been too thick..recheck your filters also make sure they are set in good and if so put the old ones back in to see if its the filters that is the problem

check your air filter housing you could of left it slightly off may not be clamped on completely

when l replaced the air filter in my car it sounded loud for a while but then it stopped and this was just a normal nonsporty air filter maybe its the same with your car that might just be what it sounded like new

Is it the right size air filter and is it in properly? What kind of oil are you using and is it at the proper level?