You have the situation fully under control -

350rpm as idel?... no way... have you checked your rev-gauge?
The lighted flywheel does not allow for this... you need either the old heavy flywheel, or its equivallent in a pulley driven car alternator...
350rpm idle would make any R25 owner green of envy -

600rpm is ok - I prefer that over 800-1100rpm as the factory setting is supposed to be. To be able to get a steady idel at below 800rpm (especially under 700rpm) you will need high-flow inlet valves, dual-plugging and retarded ignition timing, and infact a higher compression ration also facilitates the beemer low-rev idling (my experience only, and only two /7 engines).

350 is a bit low... do you have an oil-pressure gauge installed?
I have used car-gadgets untill a year or so ago when I changed to hydraulic:
Swedol items
http://handla.swedol.se/images/large/HK-3011.jpg

If the oilpressure drops below 2bars I'm getting uneasy... and all "cheap" engine oils, espcially fully synthetic, gives a reading of 1-1.5bars at about 1000rpm idle when the engine and oil is at operational temp (120-140'C on the engine oil). At 3000 rpm and up I have 6.5bars-7bars less the oil-temp drops below 90'C - then pressure rises to about 8kg. When the pressure fails to rise abouve 6.5bars - I condsider the oil as "worn out".
Starting pressure at minus 10-15'C is above 23bars... use 25bar hoses or they will burst (I have tested...). Currely I use 400bar hydraulic hoses since the price on them was quite nice.

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Drive Safely,
Albert