First I would pull the codes that are stored in the memory before I would start throwing bucks at this. Sounds like your catalytic converter is starting to plug-up. If you ever had someone stick a potatoe up the exhaust pipe, you know what I mean. Usually I can tell by placing my hand at the exhaust pipe and checking for flow, another sign is that rotten egg smell. Maybe the muffler is coming apart inside blocking flow. Most muffler shops are going to install a universal cat and if you are handy so can you! Don't be lazy, check the stored codes first and troubleshoot from there. But my money is on the cat, Steven.