My mazda was running fine and all of a sudden it started making a loud moaning/roaring noise. After starting it it idles fine but once reving up to about 2000 rpms the noise starts and after driving it doesnt want to run unless u keep the rpms up any ideas???????? Help plz!!!!!!

 

It could be a number of things, Clay.I'd look at the cat conv and the EGR valve first though. Make sure neither is clogged.