question about timing

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i am doing a little tuning to my 20b only for vacuum and for run in purposes and i saw that my LTX12 has the stock map inside about timing that goes 5 degrees at idle and all the way up to 4000 rpm stays at 9 degrees with 10 degrees split, i search a lot and i find that it is (i think) way to retard.......am i right? should i alter the timing to about 15,20 degrees at vacuum?and with what split? in order to run in my 20b street port with stock twins for now................
Thank you
Dimitris
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