You have to disconnect the air tube that leads from the filter housing to the throttle body. Then have someone at the wheel, controlling the gas pedal. Then with the engine idling, spray the stuff directly into the TB. I held open the metal flap to really spray inside the upper intake manifold, since even when it's revving up my TB flap doesn't open all that much.
Should the TB flap open a lot more on a 4.0 OHV?
Anyway the helper can rev the engine some, it helps to do that, otherwise it might stall out from the spraying. That's ok if it stalls, retstart the engine and continue. Also, your "Check Engine" light may come on during application, and this is fine, it's just spray and carbon blowing by the O2s and EGR (if you have EGR (93 and later)). The carbon will blow out. After spraying, shut down the truck and let it sit for 5 to 10 mins. Then start it up and drive it pretty well; I mean take it out on the highway, for example, and get on it pretty well.
When I did it, I remember I noticed an immediate improvement in throttle response and power. I got to the I-55 ramp, and gunned it, and went from about 20 mph to 95 mph in short order. My truck had never gone 95 mph before. I was surprised when I looked down at the speedometer because it got up there so easily. Before, the engine didn't like it above 85 mph. Now it doesn't strain at all at 95. I had to slow it down, I didn't realize I was going so fast, because it felt so effortless compared to before.