The 1.5" inlet will be restricting the flow a little. everyone over here fits 3" snorkles. 7" square coss section vs your 1.75" square cross section

I'm the odd one out fitting a 2.5" snorkle as the air box inlet is 2.5" it made sense to me.

Cranking up the fuel, I'd need to take a photo for you or scan a diagram, but this may help.

http://www.tstproducts.com/pump_adjustment.html