A4 choice of spark plug?

Hi all,
The car is a 2001 A4 Avant 1,8TS (older chassis, 180hp). Chip is factory stock, no after-market reprogramming. Plugs installed are NGK PFR6Q.
May I ask for input on three questions:
1. Are there any of you using the abovementioned (PFR6Q) plugs? Or is the NGK BKUR6ET (I think this is 3-electrode) more popular?
2. Of those of you who have tried both, which has worked better? I am investigating a possible (though sporadic) predetonation issue and am wondering which of the plugs is more predisposed to causing this, if any of them.
3. I notice that the join between the long ceramic section (where the coil boot fits) and the metal section has gone brown-yellow. Is this normal or is this an indication of too high temps? Plugs have run for 15,000 km (approx 10,000 miles).
BRgds, Robert Gothenburg Sweden
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Check out this post about spark plugs on AudiWorld: http://forums.audiworld.com/a4/msgs/1541554.phtml
I know you're not chipped, but there's some useful information there anyway. Personally, I've been running the OEM NGK PFR6Q, both when stock and when chipped ('01 1.8TQ with GIAC), and have had no problems so far. Granted, I only have 30K miles on the odo...
Cheers,
Pete
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Pete wrote:

----cutting earlier stuff

Thanks Pete, I pulled the plugs (PFR6Q) and found them to be slightly sooty, and gapped at 0,65 mm / 26 thou (should be 0,8 mm / 32 thou). I regapped at 0,8 mm, though being careful to not knock off the platinum thingies. So far my predetonation problem has not reappeared but this must be sheer coincidence. I cannot see how a larger gap distance would reduce probability of predetonation.
Would it?
Unless the smaller gap caused a too cool-running engine, which might cause carbon build-up in the cylinders which in turn might increase risk of predetonation . . .
To address the excellent article you referred to, I might try the copper core plugs if my predetonation problem returns (despite the fact that I am running only 0,7 bar boost and not the monster 1,5 bar boost that the author - and others - are doing ;-)
BR /Robert
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