My combination is similar to yours, the details are on my webpage.
The stock EEC ignition curve is a poor compromise for an Incon and all other turbo systems.
I've sampled base timing between 5* to 10*, and know the shortcomings of each.
I can run 5* base on 91 octane (the highest available here) safely at 9# boost in 100* heat. But, the engine is not as crisp and responsive at lower rpm's at this setting. Power at high rpm is also lacking.
If I set base to 10*, I experience detonation at 3000rpm under the same conditions. But, the engine is much more responsive off idle, and the increased power above 4500rpm is noticeable.
Turbo engines need a timing curve that reduces mid-range advance while leaving the low and high speed timing alone. I suggest you contact Brian Renegar (his link is on my page) to see the progress he's made in solving this.
Unless you have a Tweecer, custom chip, or other method to modify your timing curve, don't make the same mistakes I've made -- be safe and begin your tune conservatively.
I'd get some kind of tweecer, set it to 20 total at torque peak, and add some back up top.
If you're not getting a chip/tuner, then I'd set base at 8-10degrees, and start with the boost around 8lbs and work your way up. With no chip/tuner, FMUs actually work pretty decent. I had good luck putting the fp at 60 at full boost with the FMU. When I pulled the FMU it wanted to detonate, so I had to bring the timing way down up top via tweecer.
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