Sorry I haven't updated. Work has been keeping me over so by the time I get off it's dark out. Got a day off coming up in 5 or 6 days so by then I will know. Quick question though. So I changed the what appeared to be stock lifters after they started doing this exact thing stated in the op. So after I changed them out they were good for a while. Now they are doing what's stated in the op again. And after I changed out the stock volume oil pump to the HV it still happens but not as harshly. This still could be caused by the o2 sensor? Or is my engine just worn out?

 

It's likely the sensor, or a failing cat. Try the test, see what happens.

 

Got a chance to try unplugging the O2 sensor. Got about 15 miles and same thing happened.

 

Your CAT is probably plugged. Remove the O2 sensor and test again.

 

Yeah so it's looking like I need a new cat. So I found a kit with the down pipes and the cat for $300 seems pretty good for price. What O2 sensor should I get? An ntk sensor?

 

Yes, the NTK is a good O2 sensor. I'm glad you have it figured out.

 

So bumping the thread. Took long enough but finally got my new cat installed. Was able to drive about 150 miles no problem but on my way to work the other morning it started up again. Same exact issue with a brand new cat and ntk sensor. I'm starting to wonder if it's the fuel pump. You can feather the gas and you'll get some rpm but if you floor it nothing happen but some spuddering and backfires into the intake it sounds like.

 

Yeah, think I would be checking fuel pressure......

 

So I picked up a pressure tester at harbor freight and what I saw was on the driveway it fluttered between 39-42 psi and if I reved it it stayed at about 40 but I am noticing the pressure dropped 5psi after shutting the truck off.

 

So after an hour for leakdown it dropped to 28 psi