Ignition timing for deceleration? effects of retard / advance

It's a RB26 with G4X.

what's the most typical ignition timing for deceleration? I have mine at 30deg advance now across the whole range for decel.

for a factory like engine braking effect, what would be the best setting?

I don't want any exhaust pops, just a factory like feel

Hello a normal range for this would be 5 to 10 degrees less than the cruise timing so if you had 40 degrees at cruise then 30-35 deg would be what i would expect to see there

Regards Ross