Paul,
It's not as easy to remove the intake tubes on the hexhead/camhead engines as on oilhead engines. Instead of screw clamps BMW used a type of reusable CV joint clamp that requires a special tool to remove and replace it. I found one of the tools on Amazon for about $15 or so.. it's made by Lisle (same one the BMW dealer had actually.)
The rubber tubes - unlike the oilhead tubes - do not extend into the airbox, there is a tube cast into the airbox that it connects to.
It is quite possible he has some oil in the airbox. Unlike earlier bikes, there is no oil drain in the airbox. I suspect BMW thought the crankcase vent would suffice for that purpose.. it comes off the left (port) forward corner of the airbox and goes straight down to the left side cylinder head. But - I have seen oil buildup in the airbox if the engine is overfilled. The bottom of these airboxes is molded to closely match the contours of the transmission.. meaning there are hills and valleys in the bottom. The valleys can fill with oil which won't drain back unless you lay the bike on it's side. I had what appeared to be a transmission output seal leak on my bike - that ended up being oil seeping out of the airbox and running back along the top of the transmission, dripping eventually down on the forward edge of the front swingarm boot. Sopping up the oil with a rag on a stick through the air-filter opening "cured" the leak.
It's possible his is leaking/seeping at some other airbox joint that isn't really visible and eventually ending up down on the exhaust. I'd suggest that he find someone with a borescope and take a good look at the inside/bottom of the airbox. That's how I found the oil in mine (Harbor Freight borescope works just great for this sort of thing.. bought it for the Porsche, used it for lots of other things now.. was on sale for $89.)
Don,
thanks for the input. I'll locate a borescope and follow up on your suggestion.
73516