Few questions.
1) For preventive maint. purposes, when should you consider changing the fuel injectors? Truck doing great as is; just wondering when to change.
2) Will "upgrading" to performance injectors, will I see a MPG drop/change?
3) Are the injectors simple to change? (backyard, regular tools, straight-forward?)

Looking at a set of 6 used JAMMER 8 HOLE Injector Nozzle Tips ($150). Thoughts or recommendations?

 

There shouldn't be a reason that you must replace cummins injectors. To enhance performance and/or gain mpg then, yes. I went straight from factory bosch inj to Mach 1.6. From what I've heard the Jammer injectors/nozzles run dirty and produce smoke. In all honesty, I read tons of info on here in regards to injectors and installed the mach due to the fact there was not one negative comment and if any issues came up, the service was excellent. In the injector department the Machs are definately not the cheapest but you get what you pay for. JMO Yes, they are pretty easy to change out w/normal hand tools.
Ohh, and I gained about 90hp, very minimal smoke and 2mpg!

 

How many miles on the injectors? Stuff does get dirty, the nozzles get worn, damaged, carboned up, the needles get dirty, gunked up. You using fuel conditioner? The seat pressure changes.

Yes you can gain fuel mileage/power by running aftermarket injectors.

 

Injector guys tell me to change them every 200,000 miles, nozzles get wore, hard starting and smokes more.
I just changed mine for the second time, does make a difference.

 

You don't have to change them. You can pull them, take them to a shop and have them cleaned if you're happy with the overall performance of the truck. Cleaned injectors will likely give it a bit of its power back as well as mileage.

 

Running injector cleaner once in a while would probably help too?