Why the need to drain coolant when addressing/replacing fuel injectors?

I have 2001 4.7 liter Tundra TRD with right at 150,000 miles. I am the second owner since 87,000 miles, and have been meticulous with preventive maintenance and recommended interval remove and replace items (all fluids, timing belt, serpentine belt, shocks, struts, sway-bar linkages and bushings, etc.). My truck recently developed a surge(?) or more like a dead spot under normal acceleration. The power just seems to stop completely until I lift my foot from the accelerator, then all seems to go back to normal and runs smooth as silk. **No check engine light** The truck seems to act like an old 4-barrel carburetor car when you would mash the pedal down for passing gear. If all was not tuned correctly or vacuum advances were not working correctly, the carburetor would just lug and hit a dead spot and hesitate for about 1-2 seconds until all systems were communicating with each other, then the added power would kick in. The only difference for me is that I have not been mashing the accelerator down and no recent attempts to hit passing gear. I notice the lugging in my truck when a little more accelerator is needed, mostly when accelerating up a hill or grade, and not always at the shift points, although this has occurred when the truck has decided to downshift due to the added load from the uphill grade. In reading another Tundra thread, it was noted that the transmission is not always the culprit and dirty fuel injectors or incorrect fuel pressure may be the cause. The fuel pump in the tank was replaced about 2 years ago but that may not mean anything. Anyway, a "how to" posting for removing and replacing fuel injectors indicates there is need to drain coolant? I have not looked at my engine recently but do not see where the two systems would run into each other. Is this a procedure that can be addressed in my gravel driveway? Does all of the coolant need to be drained? No garage here.

 

Check out my reponse in your other thread. Also, do some youtube vid research on some of these repairs. Haven’t heard many here/anywhere complain about fuel injectors being a problem on these models.