C-15 seems to have a miss and loss of power

My truck has been parked for a few weeks with full fuel tanks. I left out yesterday and noticed it seemed like it had a miss. It's not a really bad pronounced miss. This is barely perceptible. It seemed to clear up somewhat after driving 80 or so miles but I can just tell the motor isn't right. Power just isn't where it should be. It's not throwing any codes. All my gauges are reading normal. Boost is around 35-40 psi where it's always been. Fuel filter gauge looks fine. 2003 MBN. All new fuel lines were installed about 5 years ago. I was wondering what any of you guys would recommend to check?

 

I hope not. How much are injectors $500 apiece plus about 3 or 4 hours labor? I hear you guys say remain injectors look pretty bad and can be a crap shoot. Can you get brand new and is it worth it or just go with reman and take a chance? At least they will warranty them for a year.

But before jumping to expensive conclusions... I was going to replace the secondary and clean the screen in the primary when I got back home. I was going to dump some fuel treatment in when I topped it up next before going home. Probably need to replace that o-ring in the primary it hasn't been replaced in many years. Maybe sucking air? I dunno.

###### I didn't need this. I just hope it's something that can be found. I was reading about somebody on here with some kind of problem like this that nobody could find the cause..

 

All 6 injectors were replaced in a platinum inframe about 5 years and 250,000 miles ago.

 

One other thing. I can't tell it's missing at idle even if I bump it up to a 1,000 rpms. That's how slight it is. I don't think I noticed it when I bobtailed it on a test drive during those weeks when it was mostly parked. It was only when I had my trailer and left out yesterday that I could tell. And then loaded. But this miss is slight and I hesitate to call it a miss but that's what it feels like. I know what they sound like when you have a bad injector and are missing noticeably. This seems different but then again maybe it isn't and that doesn't matter.

 

You mean an overhead adjustment? That was done less than 100,000 miles ago.