Don't know the size with stock pulleys right off hand, but you can get a piece of string and route it around like the belt is gonna go. Undo it, lay it on the ground, and measure it. You might wanna subtract .5 or so to take the tensioner into consideration.
No, The pump does not add air to the combustion chamber, it adds it after. The holes in the back of the head run to the exhaust port, and the other set of lines run to the converters. The computer does not use this at all.
The only issue is getting codes for the system not being there (TAD/TAM,I think), but those
can be turned off with a chip