what do you have done to your head?? i see a brand new head in your sig with a thicker gasket, do you have stud anr rings in there as well, if not i would not take it past 16. 5 deg. of timing, it will blow your head gasket due to spkies in the cylinder pressures. be careful, timing will help your situation, but you need to have the head done right to run the advanced timing.
wes