Newbee needing a little tuning help

Just wanting to get a good base tune in my car prior to Dyno tuning it. I have made a couple changes in the tune already but really need some more expert knowledge on a couple things. I am working on my 2017 Chevy SS sedan with the LS3 and a 6m trans. Installed long tube headers and catless mids. I am adding a VCM intake in a few days as well. Turned of codes to rear O2 sensors and brought in PE sooner. I am not sure where to go from hear. I know timing is a good power adder in these but how much and where? Also leaning out the fueling at wot after about 4-4500 rpms is good but again how much? Any help would be appreciated.

If you didn't disabled COT, the rear o2 sensor test and cat test in the engine diag tab, do those now. (some computer may not show both tests).

You can't really just wing the timing if you really trying to make good power. Save that for the dyno if you truly want to get everything dialed in there. Past that it's purely a guess on the street and it comes down to experience to know what is okay to keep things safe.

If you don't have a wideband o2 sensor, don't even bother changing anything fuel related. I'm sure most shops will try to lean it way out to 12.8-13.0 because "that made good power" when in reality if you keep it safer around 12.3-12.5 commanded AFR you will still make great torque and not have to worry about running it on the edge for that extra 9 horsepower and internet show off points.

I have the cot off already and no mil for p0420 and p0430. I have tuned my GTO with a predator and a wideband. At wot from 1500-4000 my afr was 12.5 and above 4000 brought the afr up to about 13. Had a very smooth graph on the Dyno and made good power. Trying to get a few things dialed in before I go to the Dyno and I know these are very rich all the way through the rpm range. I am just not as familiar with HP tuners as I was with Diablo sport. I used the new I2 tuner on my car but it did not have the same capabilities that the old predator did. This made me switch to HP. Been doing a few online searches for info but I start worrying about who you can trust to guide you in the right direction.

You must be a FFDP fan.

To clarify the GTO was Dyno tuned and I am getting the SS ready to Dyno.