MSD set ups
Are you asking why it dips between 4000 and 5000 rpm?
The answer is because I was told by LXmodguy that these motiors are prone to detonation around this rpm range, so I kept the timing curve safe in this area.
These motors are not old iron headed open chamber motors - they require very little timing sdvance because of efficient combustion processes - you will find the timing curve for an LS 1,2 or 3 would be similar.
I havent experimented bringing the total timing in earlier - but its something you can experiment with on a dyno.
I have no idea what you mean by your comment "in combination with MAP signal" -
All I can say is that high MAP is achieved in WOT situation, so you dont want a lot of added timing - eg at 11 psia my MAP advance is zero.
AT low MAP - for example at 4psia during cruise or light throttle, you can add MAP timing To improve fuel economy -
BUT - there are conflicting opinions on what a safe total advance is at cruise...some say 30 deg, some say 50 degrees -
Personally I wouldnt have total advance at low MAP cruise higher than 40 deg.
And as stated - at high MAP WOT conditions, mine stopped making power at 28 deg total, with nil MAP advance