99 silverado issues misfire/lean stumble?

[Team Addiction]

Hello all,

Got tired of pulling my hair out and figured Id ask for some help. Ive got a 99 silverado that has been losing power for awhile. She used to rip the tires off but not anymore LOL
At this moment it wont get out of its own way. in P if revved it falls on its face until about 3K then it smooths out but still not the power it should have at all. Seems like its misfiring or lean stumble?? WB02 showed a perfect idle (14.5-7. But showed lean under load 16.5 or so. However Im inclined to believe its spark related. False lean reading maybe due to misfire??

Newer fuel pump, plugs wires in last 15k, new fuel filter last night. Idle pressure is 50psi and 58psi with reg disconnected. Pressure also jumps to 58psi as soon as you hit the gas (in park)

Problem has been intermittent for at least a year just has to be fixed now. Previously the wife was driving it and she grandmas it so it wasnt showing the problem much. Recently my toy car blew a tranny so Im driving the truck now

Was driving through some road construction and hit pavement tried to accelerate and she just wouldnt go till it kicked down then it seemed like it was a 4-cylinder?! Also in the past the problem has existed when cold only went away with warm up.
Watching the scanner I did see KR to 2-3 degrees on throttle blips. But none under accel.
Any and all help appreciated!! Im at a loss at the moment

[Team Addiction]

Well I tried logging misfire and the only time it showed any was at the rev limiter so maybe were back to fueling?? Even though pressure is good even jumps to 58psi when attempting to powerbrake LOL Dumped some injector cleaner in the tank just for good measure. tested all plug wires their good too.
Reflashed with a bone stock file. Had a code come up for the rear 02s now that they are turned on again LOL So will cut the cats off Monday and add in a piece of tube to eliminate a clog issue. Thats about where IM at for now.
Any suggestions welcome Thanks.

[mogyver69]

Well I tried logging misfire and the only time it showed any was at the rev limiter so maybe were back to fueling?? Even though pressure is good even jumps to 58psi when attempting to powerbrake LOL Dumped some injector cleaner in the tank just for good measure. tested all plug wires their good too.
Reflashed with a bone stock file. Had a code come up for the rear 02s now that they are turned on again LOL So will cut the cats off Monday and add in a piece of tube to eliminate a clog issue. Thats about where IM at for now.
Any suggestions welcome Thanks.

Just wondering if you still had this truck or if maybe I just purchased your troubles. LOL I live in Post Falls Idaho and just purchased a truck with all the same symptoms and it just happens to have a HP tuner kit in it and the cats removed...... The guy that owned it is in spokane, WA. If I dont happen to own your old truck... Then maybe you could tell me what ended up being the cause of your troubles. Other wise Ill let you know when I figure it out... LOL

Im leaning towards a faulty fuel pump!

If you are the previous owner and have acess to the hp tuner Id love to know what the settings were set to and if theres anyway to put them back to stock...