Im not sure if your 2nd drawing will work as it doesnt really bypass the original IAT sensor wire.

This one works if you flip switch 1 to cause an open circuit and then flip switch 2 to close the circuit and send the signal altered by the resistor to the ecu.


edit: and to answer your question about your 2nd drawing. You aren't interrupting the signal sent by the original IAT wire with just that 1 switch. So it wouldnt actually *change* the voltage reading sent. So, no..I do not believe your second drawing would work.