$0D TBI build - spark problems

[dzidaV8]

Hello, I'm having some issues tuning my fresh built engine.
Engine specs:
1998 L31 Vortec bored to 355cid, flat top pistons,
LT4 HOT camshaft,
GMPP TBI intake, 61lbs injectors (for now).

I'm using '427 ECM, xdf and adx from this site (attached). The problem is that commanded spark advance is about 10* lower than values in Main Spark Tables. When I set main spark bias to 0, the values start to match. XDF has bias value in conversion formula. How is this possible? I zeroed all the other spark tables I could find, and set all spark multipliers to 1, still the same.

Another strange thing happening is that when I zero the main spark bias and have proper spark timing, the engine will idle for a while with spark values that match the main table, then it starts to retard timing to negative values. When i rev it a little it will go back to normal values and after a while retards again. I can't find anything that would do this in my bin.

I'm using the attached modified BJYL bin with stock 98 vortec spark tables.

Thanks for any help!

EDIT: One more thing - my IAC is not working and it throws IAC fault code 35 and MAP high code 33. MAP is good, only it idles at 70-80kPa when the timing gets retarded and it triggers the code.

[1project2many]

Does the ADX match the engine distributor setting? What is your base timing with the Bypass line disconnected?

[dzidaV8]

Yes, ADX has 0 offset and there is 0* initial timing set in the bin. Distributor is set to 0. I think maybe something is wrong with ingnition itself because with EST disconnected the engine won't work, and it did when I was setting the timing. I'll try to relace ignition module and set base timing to 10* as I read is recommended for vortecs.

[1project2many]

If that's the tan wire with the black stripe, yes, the engine usually runs with that unhooked. You don't need to set the distributor at 10 if the engine starts and runs with it at zero. If you set the distributor at ten be sure to change the reference angle in the calibration and the ADX.

[dzidaV8]

I fixed other problems I had, but one thing remains. I have base timing set for 10* with bypass disconnected. Initial spark advance is set to 9.8* in bin. ADX definition has +9.8 adder for spark advance retard. Main spark bias = 9.8*. All spark tables in XDF subtract biases. When set like this, the displayed spark advance is exactly 9.8* less than value in the main table. Displayed value matches what timing light shows on balancer.

When I set initial spark advance to 0*, then displayed values match what is in the table and timing lamp read is also correct. Same thing happens when I zero main spark bias.

What am I doing wrong? The engine works well with initial spark advance set to 0 instead of 9.8, but I don't like to leave it with this workaround.

Bin and definitions I use are attached.