I always play with the rule of thumb being that your ignition advance get back to 10 positive degrees and if all things are positive... Fuel octane, boost, intake air temps then you should be able to advance timing to around 14 deg! Advancing timing means you give the mixture more time to fully combust and therefore give you more power in laments terms.
So far your looking at one big thing counting against you for timing advance, and that is your high inlet air temps. I'd hate to see what a full 1-4 gear pull would look like if only one gear heats that air temp up like that. It's normal though but I guess I'm used to my meth lowering the intake air temps