Best Aftermarket CAT Performance parts?

Whats the best place to get parts for a 3406E. Truck already has some PDI parts (turbo manifold ecm) on it and I think I'm having some injectors finally giving out. Just going to replace the whole set and may as well put some in with a little more fuel while I'm working on it.

Also anyone ever had a cat injector go out in 1/2 a day? Got it back after replacing my 2nd injector and ran great all morning sounded great, then about mid day seemed to develop the same miss in it, about 1400-1500RPM at 1/2 throttle is the only time you can feel it, same as before. Don't know what could of caused it? I don't get fuel on the road always out of my barrel at home, run 2 fuel filters changed every 25K. My fuel milage is down quite a bit as well. I dont think fuel treatment would cause it, but I've been using schaffers cold weather fuel treatment for the first time this fall/winter.