this works for me and no damage done to anything...... hockey tape. first put all the tubes on the mod and the cover on the atty. then take a piece of tape and wrap it tightly on the atty just above the air control ring. then another piece on the mod just below where the atty and mod meet but covering a part of the ring. wrap them real tight, maybe two times. there should be about a quarter inch exposed right where the atty and mod meet. now the tape gives you something to grip on and just hold real tight and turn. works for me every time. this happens on my set-up often enough and before i figured this out, a lot of cursing and bloody hands were par for the course. i suppose other kinds of tape would also work but being a canadian there are always a couple of rolls lying around. it was my ah-ha moment when i figured this one out and if this does not do the trick, your atty and mod are probably welded together. hope this helps.
coop