Sorry your atty has gotten a tight draw. How are you cleaning? For over a year I did all of my atty cleaning by doing a very soft boil for about 5 minutes. Poured them into a strainer and after a few minutes they were cool enough to blow out, let dry for a few hours, and then pulsing dry burns for 20 seconds, cool a bit, and then continue the pulsing 20 second dry burns till no "vapor" came off of the coil and/or mesh bridge (if there is a bridge).
Main point is that mine never developed tightness that required any drilling. I think it was because of the soft boiling clearing out anything that might be restricting the air intake.
I have 510, 306, and 801 that have been in rotation over a year without developing a tight draw. I retire them to the emergency box when their performance drops off. The do get "tired." I have found the boiling to be superior to sonic cleaning with any substance. I now only clean my attys via the boiling method but do clean the cartos, in the sonic cleaner, using PG, and throw them into the emergency box after a draining and blow out.
Some people use a double boiler, to keep the bottom of the pan from getting too hot. I haven't found that necessary but it is a good idea.
BTW.... some sellers of attys don't recommend boiling. Way back I discussed this with them and they agreed that boiling and dry burning was a good way to clean (most attys) but many people don't want to practice the finer skills of doing it properly or can't perfect the skills. So that method is usually not recommended. We have a remarkable track record for using attys for a very long time and it is very rare for us to lose an atty to popping, burning up, etc.. I think part of our track record has to do with the way I clean attys and my skill at doing dry burning correctly. I've popped only one atty dry burning and it was because I pushed it, an almost new IKV LR 306, beyond my limit of 20 seconds pulsing.
Alice