Adam,

   You can attempt to clean them yourself, but there is always a chance
that the injector cleaner will make it back to the fuel tank. Injector
cleaner is pretty nasty stuff. It has to be, in order to get the injectors
clean. I have seen some issues with a vehicle needing a new fuel pump, after
injector cleaning (Usually on a higher mileage vehicle). Not too common, but
it dose happen.

   I have devised a plug that I insert in the return line, that doesn't
allow the cleaner to get back to the tank. There is no way to pinch-off a
return line on this vehicle.

   If you try cleaning them yourself, I suggest you have a full tank of
gasoline. This way,... any cleaner that gets back to the tank, gets diluted
well.

   As for the TCCM,... your out of luck. I don't know of any "easy way" to
shift the transfer case, without it. I suppose if I looked through the
schematics, I could find some way to make the transfer case shift, but it's
not worth the effort. This automatic transfer case is electronically
controlled. The TCCM is on a communication buss with the PCM (powertrain
control module). I have a spare module at home, but I'm not willing to part
with it. I know that one day, I might need it.

GMdude