Hmm..funny idle problem, seems like a miss, but not really..

[TIMSPEED]

Lately, my truck has been idling really funny. It won't hold an idle worth a crap! It seems like it's missing, but it's not a consistent thing. It's like the truck loses power for a split second, but only randomly, without pattern. (Like if you disconnected a spark plug, it'd always miss in that same spot.) So, it's hard to say if it's my carb causing me problems, or my plugs are already fouled. (They're almost a year old bosch platinum's with maybe 3k miles on them; although I've been running pretty rich, so that may have slightly fouled them)
Also, when it cuts out, it affects everything. Like, if I have the headlights on, the tach light will dim when it cuts out. It's very split-second though, like a "blip". It's only while it's in drive too...when I put it up into park (park idle is about 950-1000) it's not even there, but when I drop it into drive (drive idle is about 750) it's there.
Any ideas?