Back pressure GMC Sonoma 1999?

[mdsaco]

My Gmc Snoma can hardly get out of its own way, backfires and lots of back pressure on the highway. can it be the O2 sensor or EGR valve or both,,
Cde reads three things cat, O2 and Egr valve
The EGR and O2 sensors are cheap to fix the cat is expensive, there is plenty of exhaust coming out of pipe when it idles and rev eng and the cat is not too hot after a 15 min drive.

 

[Molson02536]

My Gmc Snoma can hardly get out of its own way, backfires and lots of back pressure on the highway. can it be the O2 sensor or EGR valve or both,,
Cde reads three things cat, O2 and Egr valve
The EGR and O2 sensors are cheap to fix the cat is expensive, there is plenty of exhaust coming out of pipe when it idles and rev eng and the cat is not too hot after a 15 min drive.

Here is another information that you may want to look in to.
http://members.shaw.ca/betterthanyoutoo/Sticking Poppet.htm

Keep us posted and hope it's something more simple.