We strongly recommend NOT cleaning the fuel injectors unless they exibiit problems.  The most common cause of injector plugging is mechanic's shop rag lint from cleaning them.  I simply remove them one at a time every other year and place a very small amount of anti-seize on the threads and re-install them.  I've not had a plugged injector in YEARS.  Don't touch 'em.

As for the engine monitor, there is nothing you can put on an airplane that will help save your enigne and your life like an engine monitor AND knowing how to interpret it.  I have seen enough saves that I will no longer make an IMC flight without a working engine monitor in the airplane.  We have a growing file of saves by pilots who have paid attention to their engine monitor and known how to interpret the data it is displaying.

If you have an engine monitor it is very easy to tell whether or not you have a plugged injector that needs cleaning.  Without an engine monitor, you have no clue.

Walter Atkinson
Advanced Pilot Seminars

well believe it or not there are several reasons to clean the injector nozzles.
if you are experiencing rough running engine it can be caused by partially clogged nozzle which can and does happen.  this will cause an excessive lean condition in one cylinder.  that alone is a very good reason to have a multiprobe engine analyzer.  that device will tell you if it is a problem with the spark or the fuel and it will tell you on which cylinder.  it will also let you know if your cylinder is getting too hot so you dont cook it unknowingly. (I personally like the JPI EDM-700 or better version) the other reason is if you notice any blue or black fuel staining around the injector.  this indicates a leak which is an indicator of a partial plug. I have never used a shop rag to clean the nozzle.  cant imagine how I would get it in there as its a mightly small hole.  I use a ultrasound machine and a bottle of gunbore cleaner solvent.  they come out as shiny as new.  I then reinstall them with a bit of FuelLube on the threads.  never have had a problem doing this and I cant imagine why it would be necessary to remove them simply to put antisieze on the threads.  you wouldnt remove your sparkplugs simply to put antisieze on them would you??  and if you have GAMI injectors dont forget to make sure you put them back in the correct cylinder. 
I agree with Walter on the importance of the analyzer.  it will be the best $2K you ever spend.
thats my 2 cents worth.
mark

Mark:

I have a few comments in response to your last post:

1) If you do have an engine monitor, you will know if an injector is clogged.  If the F:A ratios are proper as seen on the monitor, they are not clogged and there is no need to clean them.  Period.

2) The blue stains are NOT from an injector being clogged.  They occur after shutdown!  Some of the excess fuel left in the fuel lines boils/vaporized out through the screen of the injector.  This is normal and not something to be the least bit concerned about.

3) The shop rag lint gets in through the screen!  It's from wiping the OUTSIDE of the injector off.  It's the most common cause of a partially plugged injector.  If you do not have a monitor, and you clean them at annual, how do you know that you don't NOW have a clogged injector from the maintenance??

As an aside, I've not cleaned an injector in the last three TBO runs.  Never.  (I run avgas through them during the entire time the engine is running and that keeps 'em clean.  Avgas is a pretty good solvent!  <g>)  All I do is remove them every-other year, re-apply anti-sieze and replace them.  I would only clean them on condition that it has shown itself to be plugged on the engine monitor.

Walter

Walter,
I'm sorry but I'm not trying to pic nits here but I will agree with everything that you said except the part about the blue stain being normal.  if blue stains on the outside of the engine are considered normal then I've been doing something wrong all these years.  and perhaps I should advise all my customers that DOnt have blue staining that the engine isnt operating properly due to the normal blue stain not being evident.  and the part about the rag causing a problem is a valid point however if the mechanic left the rag in his pocket then there wouldnt BE a problem.  personally I dont see the need to wipe the nozzle after cleaning.  that would be like using a towel to dry off with before taking a shower.remember that yes avgas is a decent solvent however, thats not all that is in the gas. it is not pure. remember the lead ??