2005 sts v6 loss of power and weird noises after cold start please help!!
 

Hello everyone, Im new to this site and was hoping to get some advice and/or feedback from people with the similar problem. I have a 2005 Cadillac STS V6 with 235k miles (still runs great!). Just had the cats replaced. In the morning when I start my car, sometimes it'll tell me to "service engine soon". Then the display will read "reduced engine speed" and i will not have power AT ALL. After the car warms up, its FINE! I also notice a weird air muffle sound that sounds like it's coming from the air intake system (either the airbox, or the throttle body). It almost sounds like popcorn. Any help would GREATLY be appreciated. THANK YOU :D