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R1100s - wandering idle speed

Hi to the Group,

First, apologies for this war story being told in kms rather than miles.
50 miles = 80 kms. My 1999 1100s now has 207,000 kms on the clock and
still going strong.  My daily commute is 100kms, averaging 550kms per
week and ridden "firmly-plus" rather than pussy-ing along.

Had my favourite BWM dealer install 2 refurbished throttle bodies a
month or so ago because of general wear (rattle) and idle speed
increasing with engine temperature from 1100 (cold) to 1450 or so (hot).

The LH replacement body (the one with the throttle sensor pot) shaft
seized at 75% throttle during a 300kms drive a week or so later.
Managed to drive 40 kms in 3rd gear to the next petrol station to look
into the problem.  Shaft was stuck as "tight-as" !  Squirted heaps of
WD-40 in the general direction of the inside LHS shaft before it
eventually freed up enough to drive the remaining 150kms home.

Took bike back to shop and NFF for the shaft sticking. Bugger!  (Side
issue - petrol tank managed to get a gob-full of water in it after shop
washed-hosed bike down to clean it.  Power response vvs throttle opening
was now interesting ...)

After this, idle speed wandered all over the place - hot or cold.  Took
bike back to shop - this time, LH "rubber gland" joining throttle body
to engine body diagnosed as leaky (could be seen visually).  Both LH &
RH gland replaced. Idle speed now fairly constant long-term whether cold
(1100) or hot (1200). However, the idle speed wanders all over the place
over "seconds" hot or cold -  idles averages 1150 then rises to
1250/1300 in 2-3 seconds - holds - then down to 1100-1050 for 3-5
seconds - holds - then up again etc etc.  (The variations are a "tacho
pointer width" or more.)

1)  Idle issue - What's the likely culprit ?  I don't have access to my
TwinMax right now.  What should I be looking for or replace ? 
2)  Water issue - Put a cupful of Methylated spirits into the fuel tank
to try and soak up the water but not entirely successful, particularly
when the low fuel LED comes on.  What now ? Drain the tank & replace the
fuel filter ?  (Aarrrggghhh !  both nasty jobs.)

As a complete side issue, since all this has been going on the bikes
roll-on torque has increased noticeably ....

Many thanks - all ideas gratefully accepted.

R1100s Mandarin