Noob Timing Question? high idle light miss fire

[ShouldaHadaV8]

I've noticed with my timing light that my timing advances more under throtlle although my base timing is at TDC and it idles at 20 BTDC. What would make it advance like that? I've already tried resetting the timing and tried more/less teeth on the distributor. The motor is idling high around 1000-1500 and slightly miss firing. The TPS is 2ohms at idle 10 at WOT, No air leaks, etc.