Hard Warm Start on '92 525iM

[BlackOnBlack]

Occasionally my car will take many attempts (6 or 7 times cranking at 3-4 seconds apiece) to start when warm. It's been happening since I got it a month ago. Some days it works fine, others, it happens numerous times. It just had a valve job about 2000 miles ago (at 141K miles) when I bought it. Mechanic said compression is good. Gas mileage is good (~20-21 mpg-all-purpose miles) Runs perfectly well. General idle is smooth.
When it finally fires up, no smoke is evident out of the tailpipe. No excessive fuel odor. If it were a carbureted engine, I'd think fuel starvation. With all of the electronics, I'm not sure. I haven't yet asked the mechanic if the fuel filter was replaced.

Any initial thoughts?
Also, any opinions on acceptable oil consumption for BMWs.

[shogun]

http://www.bmwe34.net/e34main/trouble/535ihot_start.asp

[Tiger]

Yep... Checkvalve.