Timing guru's.... please help

[blues14]

I have an 5 speed rb20det that was originally an automatic. i know that a 5-speed rb should have timing set at 15 degrees, but my 5-speed is running off the original auto ecu which should be set at 20 degrees. i had my timing set at a shop to 15 degrees and i have a 'stutter' at 5k rpm, but if i advance my timing with the cas , the car loses the stutter. Is it safe to just advance it till it loses the stutter? its advanced by about 6-8mm right now.

[Yellow4g63]

I ran mine at 20deg cause I had the Auto ecu too. Didn't hurt anything at all.