Oh Bugger.. sorry for resurrecting an old post, I just read through this whole thread as I was looking for some information on my issue which sounds very similar, Except mine only became evident AFTER fitting new SMF & Clutch on my Pathfinder?
Before changing everything, I had some very minor clutch judder, and the DMF was knocking a little, so thought I would catch it early and upgrade.
Unfortunately I had not set eyes on this forum before I did it, so in my ignorance bought a Cheap unbranded SMF & Clutch kit from Techniclutch on Ebay, after all, no matter how cheap, it still has to meet spec right :faint
My mechanic installed it and within 5-10 mins of starting the car, I knew I had made a mistake ! the mechanic is not to blame as he just did exactly what I asked, it was his last working day before Christmas and was doing it as a bit of a favour
I have EXACTLY the same rattling you mentioned, only starts after a few mins once warm, only present at idle and goes away once clutch depressed, I have also now got REALLY BAD clutch judder and vibrations through the car when accelerating.
Looks like I was also fed a similar line of BS to you, as when I contacted Techniclutch they said things like let it bed in, rattle is normal with SMF etc etc
Now done almost 1000 miles and actually seems worse

ops
But I'm in a bit of a confused state now ?
Believing that maybe OEM is best, I have ordered a new LUK DMF and Exedy clutch kit, also new slave and master cylinders.
Really though I would prefer a SMF, as plenty of people on here have said that they have done the conversion with no ill effects and lets face it they just done fail like a DMF, But I'm really worried about this rattle ? Will it still be present if I fit a good quality SMF ? Do I need to be looking at this spigot bearing / bush, am I just masking a bigger problem if like Techniclutch reckon the DMF absorbs the rattle ? will I get really bad vibrations ? :dunno
i ordered the Flywheel & Clutch from Eurocarparts as if there is an issue again its easier to deal with my local branch than the hassle i have been having online with Techniclutch

, So It's not too late to change my order to a SMF.. Oh what to do :nailbiting
A few people have suggested taking it to Kaiser motor which I would love to do, but having already paid out once for it to be done, I cannot afford to take it to them ....