Don't adjust fuel sync to anything but 0!!!!!! Melted new cat...

 

Adjusting the fuel sync to 0 did not melt your cat, all fuel sync does is change the time the injectors fire fuel. It does not control how much fuel is being sent through the injectors. Did you inspect that cat before you changed fuel sync? I bet it was already on it's way out.

 

This all started with a distributor change due to broken cap screw. I bought a loaded aftermarket distributor. When I put that in and took truck to dealer for fuel sync adj it ran like crap. I brought truck home and swapped aftermarket cam sensor with factory one and truck ran much better but still seemed a bit sluggish. I drove it all around and plowed a full season all seamed ok. Then my factory cat broke into pieces. I replaced the cat with a new aftermarket and all was good but still seemed sluggish. I did the plenum, tune up ect, no help....Then it hit me that I did not ck fuel sync after I put factory cam sensor back in, I ck in with my local shops Snap-On scan tool and sync was 23 not 0...I set to plus 5 drove it ran a ton better but still no go under heavy load. Reset to 0 the other day still no improvement. Installed new cat today truck runs like a raped ape.

 

Glad you got it figured out. I still recommend a comp test to be done, more so now than before. Start with cyld number #8.

 

number 8 has 150..........will ck rest