Just got my 2001 Blazer out of the shop. Had check valves replaced and the t-connector replaced. Left and while driving heard a loud bang on front passenger side like something came up off the road and hit the underside of my Blazer. Did not have much power going up a hill. Used some Marvel in the gas and the power came back. Now the "service engine soon" light is on and I hear that bang at least once a day. Possible backfiring?

 

i would check your cat for blockage

 

Get the stored codes pulled and list in the order they come up.

 

@ coolasice, you were right. The cat is blocked. I was hoping that was not the problem, but really did suspect it. Oh well, would put it on myself if I had time. Found a muffler shop that will do it for $500. Ready to have it run great again!!