Kevin, many including myself have had VERY bad experiences with those plugs, below are some examples. Best of luck.
Spark Plugs - Inspection II
OE stock Bosch or NGK, NOT Bosch +4's
There has been more than person that has discovered that their Bosch +4's have "backed out" or worse yet that some or all of the electrodes were actually missing from the plug. I myself found Bosch +4's finger tight after 10,000 miles and I know I torqued them to spec.
http://bimmer.roadfly.org/bmw/forums/e39/f...?postid=3031210
Message Title: Still no fix yet. My valve covers are leaking and
Posted by: Saman on 2003-04-14 at 14:17:53
(posted from: Host: IP: 159.178.203.36)
Message: couple of the spark plugs were drenched in oil. By the way, the Platinum 4 all 8 of them the tiny electrode had dissapeared completely, like it had vaporized. Put a set of the Bosch coppers from the dealership and the car is not missing any more. However, the power is not like what it used to be. I've gotten a catalytic efficiency a code a couple of times. I am thinking that, I might have
messed up the cats by dumping fuel in them when the car was missing for some time. Once I get the valve cover fixed tomorrow. I'm chaning out the O2 sensors since they are stock and the car has 110K and see what happens.
http://bimmer.roadfly.org/bmw/forums/e39/a...p?postid=223607
Message Title: My bad 540i weird idle solved
Posted by: Mike on 2001-12-14 at 13:00:06
(posted from: Host: wwwgate32.motorola.com IP: 136.182.2.222)
Message: Hi All, just wanted to send this warning out. I had the same weird idle problem as Ken S. and used some techroline to get rid of it. But it didn't. I took it to BMW and they said no codes set customer using BOSCH platinum +4, not recommended. Bosch recommended them when I put them in but just to see I put the old plugs back in and it doesn't miss a beat. Thought all of you would like to know not to buy these plugs.
http://bimmer.roadfly.org/bmw/forums/e39/a...p?postid=237174
Message Title: Re: My 97 540/6 is same. Sometimes nearly stalls at
Posted by: Mike on 2001-12-19 at 09:48:11
(posted from: Host: wwwgate35.motorola.com IP: 136.182.2.225)
Message: I complained to my dealer, they check the codes, none and told me to get the Bosch Plat +4 out, no recommended. Replaced them with the Bosch as F7 LDCR and my small idle problem is gone. I have a 98 540i 6 speed, hope this helps.