ok i have a 2004 mazdarx8 and it was sounding a little odd the other night in the exhaust then today there is no engine light but it still sounds odd like theres not enough back pressure and it sounds more muscular.... little less power in low rpms also....any ideas

 

Cat may be clogged...

 

either clogged cat or MAYBE an exhaust leak... more than likely clogged cat though

 

Only way to check the cat is to unbolt it and look inside.

 

Please give us the history on your car. The service it's had and parts replaced. Model, type of driving it gets(long commutes), fuel used, oil type and consumption, ever flooded, red lined. Just any thing that you can add.