Having searched the forum extensivley, i still cant find any thing conclusive. this is my second go
1992-500sl

Symptoms
Cold starts - overnight, starts fine , although engine fires aftera longer turn (2-3 secs)

Afert 30 min-4hrs- takes 2-3 cranks (ignition on fr bout 10 secs).

starts perfectly (half turn ) if started withing 1/2 hr.

Things changed /checked

1. distrbutor cap, rotors, 3 suppressors
2. ignition coils (3)
3 spark plugs (3 had carbon)
4. fuel pumps/accumulator/ filter.
5. checked fr vaccum leaks(fixed leaking injector seals )
6 two doses of fuel injector cleaner .
7. no fault codes .
8. cleaned idle control valve.

I am going to get lambda tested tomorrw , as the car idles at 600 in D, but rough idling at P,N. and post findings here.

been trying to crack this fr a while , and i came across OVP as a culprit, what is the closest substitute in sl (as i think they do not have an ovp). I did jump start my car about a couple of weeks before the problem started , and dont want to leave this stone unturned.

I definitely need a pointer in the right direction , and dont want to
throw any more monet at parts that may be unwarranted.

Thanks for your efforts in advance!!!