haynes says 23-25 BTDC
didnt FI and a few others set theirs to 28 BTDC, but you have the 150bar pp injectors 2 stage
all my injectors are factory with the 256 noz , all set to 135bar
what should i set my ip to? i dont care about COx

2ed question.. turning in a new chain , shouldnt affect the ip time unless i jump a tooth / screw up right?, it should bring the time closer the way it should be right?!

__________________
1985 300D - 599,xxxk - blue interior #265 Monark Nozzle, AL129X, 15" Ronals, Gen II Big Brakes hunting
1985 300D - 491,xxxk - in prog-{A-A IC, 3" exhaust, psi\pyro, 28*BTDC, Hella Euros, IP Limiter removal
1985 300TD - 783,xxxk - parts car,used new engine with ALDA cap inplace
1987 Kenworth T-600 8LL 425 CAT Mech. - 6,000,000+k - DEI exhaust wrap, punched through resonators, 1 recent rebuild,

26-28 is the best range if you dont care about NOx emissions.

any rough estimate the % change in emissions vs performance gains overall?

Yes as the chain stretches it automatically retards cam and injection pump timing. Just installing the new chain might put it right back on.
Depends if pump timing has been changed already over time to compensate for earlier chain stretch. You really should check the chain properly for stretch if you have not as the last owner might have already changed it for example.

ive heard from a number of old benz mechanic not to change the chain because they have laid new chains never to ones with over 230k on them and the difference wasnt enough as fare as stretch...just guides and the tentioners are the things that go....anyone know if this is ture...ive seen lots of these car with chains breaking but no one can say it it was something else that went which would of course make it break.

__________________
Wie lange wird Ihr Auto leben?