I just recently picked up a 99 Silverado 2500
I have noticed it has a rough idle, but general driving it is fine
today I noticed that it doesn't want to rev above 4000 rpm and at certain points of throttle under load almost feels like it is surging.
I did a case relearn and took it around the block. Same issue with it not wanting to rev past 4k rpm. However I realized I the VCM scanner running, and it is picking up KR in wot.
The issue I am trying to track down is the fuel trims. At idle they appeared ok, but in all other locations, both the stft and the ltft went positive by a ton.
I have already replaced the intake gaskets, and would expect to see positive trims idling and them act normal if it was a vacuum leak
The previous owner had put on some horrible shop made exhaust and a cai. I used maf cleaned to clean the maf when I had the intake off, troubleshooting my rough idle
the o2 sensors look like they are switching ok, and I am not getting an cel for those. I did get a random misfire under load today, and a maf performance code when I scanned, but it never even set the light.
Any thoughts on what I should be looking at next?