Ok, so we have a classic Bosch KE depression issue. Its like a human depression issue, but easier to fix, although if left... it can also CAUSE human depression too. LOL

First thing to check is crankcase integrity, so we need a good seal on the oil filler cap and the dipstick. Crankshaft mains can cause this too, as can teh distributor seal.

If you have a dump valve, remove and block the pipe immediately as its almost always these.

if none of teh above helps, add 1/8th of a turn clockwise to the metering flap base position adjuster. (NO MORE) and see if that helps.

Also bear in mind Bosch KE requires 25% throttle during cranking. (RTFM)

Bear in mind I am looking at hot start issues, If this is a cold start ONLY only problem it could well be the dreaded failed black box. Testing that is a lot more involved.