[kr_xv]

I wonder if there is really a need for this?
Tell me why it should be done.

It depends on your approach for solving the issue, save cost till it happens and may have more downtime, or prevent it from happening and prolong as much as possible before requiring downtime. There is no right and wrong answer, it is up to individual mindset

 

[kr_xv]

thanks, kr.
I do not know what the issue is.

The issue is engine pinging, sluggish acceleration and for those have sensitive ears, noisier engine.

 

[kr_xv]

This does not address the worst problem...carbon buildup under the intake valves. I use CRC intake valve cleaner every 10,000 miles.

The Subaru top engine cleaner is supposed to do what CRC intake valve cleaner does, but as its effectiveness of liquid and foam, so far I never see any documentation showing which one is better.

 

[kr_xv]

How effective are such automotive store valve cleaners when you spray them so far ahead of the valves? Won't it just coat the inner air track surface without really reaching where it should?

All the PEA-based cleaner documentation points to more effectiveness with heatsoaking, so for CRC they recommend to heat-soak the engine at least for 1 hour after spraying it with the cleaner to have better results. Their documentation shows some carbon even being removed up till 1 week after application.
My personal regime involves using PEA based fuel system cleaner in the tank a few days before and after using CRC intake valve cleaner (that is similar to any 3-step carbon cleaner kits), as well as spirited driving after application, that I find effective address the sluggishness, noise even though I seldom put boroscope inside to take picture.