Using The Gm Top End Cleaner on a GMC Syclone
The PCV system spits oil back into the intake, carbon gets built up on the heads/valves, and result in detonation causing, raised hot spots.
GM Top End Cleaner is pretty simple, suck it in while the engine is running, let it sit in the combustion chamber for some time, then burn it all off.
There are 2 versions of the cleaner, spray, and liquid in a can. I've used the spray can, though many others have used the liquid version.
It's probably best to do this just before you have planned an oil change.
Using Spray GM Top End Cleaner
We want to spray the cleaner into the engine while it's running. You can either remove the Turbo to Intercooler pipe and spray through the intercooler, or remove the intercooler and spray directly into the throttle body.
While the engine is running begin to spray some top end cleaner directly into the IC/throttle body.
Keep your other hand on the throttle linkage so that you can open it a little to keep the engine running. It will want to stall while it's sucking in the cleaner, just give the throttle a little blip as needed.
Before the can is completely empty, go ahead and let the engine die while your feeding it cleaner.
If it doesn't die, turn the engine off.
Let the truck sit for 10 or more minutes to let the cleaner do it's work.
Start the truck up, making sure your in a wide open area. It's going to smoke a lot!