Dear LS friends, I need your help.

[Low Elco]

So, I've built a couple of trucks, done an LS swap and been working on cars for a long time. My DD is an 09 Sierra CC, 5.3/ 6spd. The DOD lifters went out at around 80k, I bought it with 96k, now it has 159k on it, and they went out again. I wanted to eliminate the DOD, so I bought a kit with a Brian Tooley "no Spring" cam, ls6 lifters, etc. I also put headers and a K&N filter on it. I got it all assembled and took it to one of the big dog tuning shops in town to turn the dod off and put a tune on it. To be blunt, it runs like ass. and they gave it to me that way with a shrug. " we dunno." They apparently had no cam sensor signal, so they put a cam sensor in. So a frined had a Blazer with a 6.0 and a cam that ran similarly crappy, and he had a guy that fixed it. so Monday, I went to that guy, at least he tried. His diagnosis was plugged cats. Still runs like crap. So, last night I rodded out the cats. Just as bad if not worse.

So, what's it doing? It idles like a Pro Stocker, pings and shudders at idle, reeks of half burnt gas, breaks up over 3500 rpm, you can feel it breaking up stumbling on the highway. It's down on power, has to kick down to pull hills it never had a problem with before. At idle it acts like a 70's car dieseling. If it was a SBC, I'd say the timing was way retarded. The gas is fresh. It has 58 PSI at idle. the plugs look identical when you pull them. After the first tune it was like they were spray painted white. IT has from 138-155 psi of cranking compression. its not throwing a code. Mechanically, it's fine. Any Ideas? Please, I'm literally at the and of my rope and I need this truck running in a bad way. Thanks.