Scoot, Can you pls elaborate on your experience? were your injectors spraying bad and did it fix them? I've always wondered about my 300SE with 235K on it whether it needed cleaning. Also I now have the 6.9 that I want to clean. Does your car run better after? I figure if I clean 2 cars worth and it works then it is worth the price of the equipment.
My situation is a bit different from yours. I'm taking a car that has been not running for 15+ years and resurrecting it. Doing that involved cleaning every aspect of the fuel system from back to front - tank, lines, pump rebuild, cleaning injection pump itself, injector lines, and the injectors and CSV.
In the case of my car yes, it runs better now than before but that's because it didn't run before. Got lots of filth out of every component.
As for the injectors themselves, there are basically 4 states they can be in:
1) clogged/blocked (which mine were)
2) spraying poorly and at too low of pressure (which mine became next)
3) spraying so-so and leaking down in pressure and leaking (which mine didn't do)
4) spraying properly (which mine are now)
I'm not sure it matters whose pop cleaner/tester you use, what is important is to get them un-stuck (if they are stuck) and then to get them to the point where they spray just a little spurt of nicely atomized fuel at around 240 psi. When they are at that state they actually make a little chirp sound. I have 6 chirpers now.
Kent Bergma (MercedesSource) sells a tester that's nice. You can find a cheaper one on ebay either from US or India. Or you can make one - also discussed on this forum and in others. For my money buying the one from MercedesSource was a good choice because a) the cost of the tool is SOOOOO much less than the cost of a single injector and b) I'm happy for Kent to make money on his business.
Your 6.9 probably has K-jetronic which isn't going to have the same type of injector and I don't think you can clean it with this type of device.
I have some pictures and posts regarding cleaning injectors in various forums:
Re: Mechanical Fuel Injector (MFI) Tester and Cleaning Kit
M189 6 piston Injection pump issue - stuff coming out of some of the lines only
Help removing Injectors from M189.986 engine....
MercedesSource has a lot of good youtube videos - I did most everything in Bergma's Resurection of the Beast series in which he is bringing a W109 6.3 back to life... Basically the same process as for a W112 M189...