225 turbo headers

One doesn't exist, you'll have to figure out your own advance curve. But you already have one - a flat 18 degree curve. Use something like Megajolt: EDIS, wasted spark, onboard MAP sensor. You can keep your 18 degrees total advance, just put 18 degrees at the top right side of the table (RPM vs. MAP). A NA slant with reasonable intake/exhaust likes 32-34 degrees total timing, stock timing is 30 degrees, all in by 1500 rpm or less. Most like 10 degrees at idle and for cruise you add in 10 degrees in the high vacuum rows. So there you have the atmospheric line of the timing chart, the cruise and high vac areas, and the high boost line of the timing chart. Then you can smooth it in from there to get a starting point.

If you have access to a load dyno (NOT a dynojet inertial dyno) it's pretty straightforward to set up an ignition map. Use det cans to listen for knock on the dyno, each run you can advance timing a couple of degrees and watch power output. Start out with your boost controller turned way down and creep up the chart. I've always had the luxury of tuning engines with a knock sensor but it can be done without one. EGT is a great timing tuning tool - EGT will increase as timing gets later. Power will also level off before you hit the detonation limit. So if you are at 18 degrees at full boost, and adding 2 degrees shows no power increase, go back to 18 or 19 and leave it there.

Anyway this is way OT, really it's not as hard as you think.