Hey ive just noticed lately that my thermal ive had for 5 yrs has gotten raspy when u full throttle it. Any ideas why its not all deep throughout the range like it once was. Stock header and a gutted cat into catback thermal is what im running. When i gutted the cat abut 2 yrs ago all it did was made it louder it didnt cause this raspy sound its got now.

 

For what its worth my thermal was raspy when I was running without a catalytic converter.

 

a muffler is not eternal,
it got some sound deadning material into it ( it's like mineral whool )
it is prolly packed up with oil and all sort of grime, so not as sound absorbing as it was when new.

Kranked.

 

Maybe the baffles are whatever they are called have broken loost inside.