I have a '95, 4.9l and pulled off the throttle body and intake manifold as part of the process to change the fuel injectors.

Both the throttle body and the upper intake manifold have carbon in them. I've seen posts suggesting soaking the manifold in mineral spirits to loosen the carbon. But given the size of the thing, it will take a couple gallons in a large bucket to be able to do so. Is there an easy spray available that doesn't harm the original surfaces? Does it matter after 200k miles?

 

Get some throttle body/intake cleaner. Works well.

 

An old tooth brush or bottle brush works great too. The throttle body and intake cleaner works well, but sometimes isn't quite enough. I know most people say not to use carburetor cleaner on these parts, but I've done it many times on several vehicles.

For the intake, I've used engine degreaser and the water hose too. I'd probably do this first, and possibly a second time, before using spray cleaner. You'll get more crud out of it.

 

I use a pressure washer to clean out my intakes(off the truck of course). With the I6 EFI upper intake design, its a pita to clean out!!!! I fill mine up with engine degreaser for a few days before blasting with the pressure washer.