2003 injector issues

[steve604]

so i have a 2003 7.3 that starts and runs fine if i start it every day
-after 2 days of sitting it starts hard and runs a little rough
-after 3 days it's a little worse
-after a week it takes about 30+ seconds to start and runs really rough for about 15 minutes

the glow plugs work fine, have the white rodgers relay in it. it blows no smoke on start up or while it runs rough. i replaced the injector o-rings a few months ago and i thought that fixed the problem until i took it on a long trip hauling a heavy trailer for a couple of weeks. after that trip it has been starting and running like i never changed the o-rings.

is it possible/common that an injector or two are bleeding the fuel from the heads?

i just missed a brand new set of injectors on craigslist for $400 and i'm still pissed about it.

-should i pull these out and take them somewhere to get tested/rebuilt?
-should i get a used set, have them tested/rebuilt and switch them out with mine?
-do i even bother to get used injectors repaired or are people having good luck with this?

if i leave it the way it is for a while..... do the piston dishes hold enough fuel to hydrolock a cylinder and bend a rod? i know that diesel is getting into the oil because i can clearly smell it.

the truck has about 170,000 rough but fleet maintained miles on it if that makes a difference.