Maybe I've overlooked it, but have you used the fuel pressure check procedure? Stumbling under load can indicate a fuel delivery issue.

 

^ and the puter does't monitor fuel pressure so it wont trip a code if its low.


Plus since you changed the cat have you disconnected the battery for 20 minutes or so. You need to clear teh puter memory. It stores information to make run based ont he last time it ran. Over time your cat plugs up, the puter compensates for it so you dont notice until one day, all of a sudden you have trouble. Then you swap out the cat, howver the puter is trying to control the engine based on old data, no start, disconnect both batttery cable so the puter loses that stored memory and it will reset to the defualt settings. Then relearn.

 

ok guys, I have this one figured out!!!

replaced the coil along with the little module attached to the back with the silver fins attached to it. (I think it is the ignition control module)

fired up, warmed up, and holy Sh**, this truck is raping the road better than ever.

as for the stumble you are getting 4x4willywill, could be a few things, minor, but..
1. check your plugs cap and rotor.
2. check your vacuum lines at the back of the intake, skinny one on passenger side rear, and fat one on driver side rear.
3.just wanted to let you know that my stumbling problem was not noticable in the beginning, but at idle, you could hear it (lobe) every once in a while. then it progressivly got worse.

this module fixed all that completely!
PS. the one that was on it was one from autozone or napa, and the one i replaced it with is OE GM part.
Not sure why the difference, but huge turnaround!!

let me know how you make out, we'll go from there.

Thanks everyone for all your help, greatly appreciated.

happy new year.