Inlet and exhaust temps.
Colder air is more dense, if you can keep the TB and IM cool, you will also lower intake temps. Which in turn gives you the potential for a bigger bang, if coupled with a stronger spark and the right AFR you can gain a few easy ponies!
As for the heatwrap, given the source of the heat is the engine and the exit is the backbox, you want it to be as hot as possible leaving the engine to ensure good convection
And as for the spacers, they're there to stop metal to metal heat transfer from the block. The waxstat is there to hear the TB in cold temps to stop the IM from freezing over in the winter . Again, deleting it removes connection to the engines coolant system, meaning it's not constantly circulating hot water through something that, ideally, should be as cold as possible
