Missing and small popping at highway speeds

[EMT96]

I've been having a problem with my 96 vortec . At highway speeds (65-70) and with a light throttle it starts to misfire and jerk a little. The rpms dont move they stay still , and i hear a little popping or backfiring. I changed the cap-rotor-plugs and wires and still the same result. I also noticed that my catalytic converter went bad . Its rattling and makes a lot of noise. Any suggestions?

 

[UrbanOffroad215]

is your engine light coming on? if so...have you had the code read?

 

[wild_chld1]

was it an after market distrubator cap ,i had troubles with that, and check ur spark plugs for cracks,i had those 2 issues with my 99 obs drivability problems