Was wondering if anyone could give me a little insight to what is going on with my 8. I have an 04 with about 80,000 miles, change oil regularly and coils, plugs, and wires where changed about 15,000 miles ago. recently i've noticed a loss in power and some lag with throttle response. The car is also stalling out after highway drives and i've noticed what use to be very loud backfires now sound very muffled and low. No CEL except for right when the car will stall out. I've tried searching around but cannot find anything that gives an explanation for the strange muffle on the backfires.

Note: i have a exoticspeed r1-t exhaust and about 3 months ago noticed my cat had fallen apart and was coming out of the exhaust.

any advice would be great. thanks alot

 

Likely a dead cat and leftovers inside stuffed up something . My car didn't wanna rev above 6k rpm when my cat started deteriorating.

 

+1 CAT failure

 

i took the cat off and its almost completely empty. any ideas on how i could check/unclog the cat back portion?

 

if you're under 80k miles, your cat is under warranty.
If over 80k, you can gut your cat, but I'd recommend purchasing an aftermarket cat or midpipe.
Just shove a broom stick or something of the like in there to gut it

 

a broom stick might not be enough. A crow bar, rebar, angle iron or metal pipe and a hammer will work if the broom stick doesn't.

 

Thanks for everyones help. Is there any way to check the O2 sensors to make sure their still working properly? Could bad sensors also be contributing to the problem?